A) Megan was doing time-trials on her bike around 400 metre horizontal track.


ii) Compare the forward force on the bike with the backward force on the bike when Megan was travelling at a constant speed.


B) Megan then crouched down over the handlebars to make herself more streamlined.

She continued to pedal with the same force as before.


i) Compare the forward and backward forces on Megan and her bike now.


ii) Explain your answer.

i think it’s asking for ultraviolet

Answer:

Ultraviolet Light

Explanation:

Answer:

scissors

Explanation:

Answer:

Let's first remember what a lever is used for... it allows one to magnify the amount of force being applied to something, via a stiff arm. Now let's go through a process of elimination.

Light switch: Yes there's a stiff arm. And although you're not doing much work turning a light on and off, the switch does magnify the force you apply to the mechanism hidden behind the wallplate. We'll call it a lever.

Knife: Acting as a wedge to force two halves a whole apart. However, it can be used as a lever too. Pushing a knife onto something doesn't always cut it right away. Sometimes, you have to put the point down and then apply force to the handle, using whatever you're cutting as fulcrum. Ultimately a wedge, but still acting as a lever.

Broom: Are you on your knees sweeping with a toothbrush, which takes a lot of work, or are you holding a broom handle in two hands, moving one and using the other as a fulcrum? Thought so. Still a lever.

Scissors: Like the knife, they act as a wedge, cutting through thin materials. However, the cutting point is right at the fulcrum of the scissors! You're not magnifying any force there. So I would say no, scissors are not an example of a lever.

Explanation:

Answer:

The temperature and volume of a gas are directly proportional when pressure is constant.

Explanation:

Charles's Law was proposed by a French chemist, Jacques Charles. The law states that "The volume of a fixed mass of a gas varies directly as its absolute temperature if the pressure is constant".

The law shows the relationship between volume and temperature at a constant temperature. It is mathematically expressed as:

                             V∝T(P,n constant)

Answer: it’s A for e2020

Explanation:

Just took the test

Answer:

66.3 V

Explanation:

The wavelength of the electron must be equal to that of the x-ray photon:

[tex]\lambda=0.150 nm=0.15\cdot 10^{-9}m[/tex]

the De Broglie wavelength of the electron is related to its momentum, p, by the formula

[tex]p=\frac{h}{\lambda}[/tex]

where h is the Planck constant. Solving the formula, we find

[tex]p=\frac{6.63\cdot 10^{-34} Js}{0.15\cdot 10^{-9}m}=4.4\cdot 10^{-24} kg m/s[/tex]

Now we can find the electron's energy using the formula

[tex]E=\frac{p^2}{2m}=\frac{(4.4\cdot 10^{-24} kg m/s)^2)}{2(9.11\cdot 10^{-31} kg)}=1.06\cdot 10^{-17} J[/tex]

Then, we know that the energy of an electron accelerated through a potential difference of [tex]\Delta V[/tex] is

[tex]E=q\Delta V[/tex]

where

[tex]q=1.60\cdot 10^{-19} C[/tex] is the electron charge

Solving the equation for the potential difference, we find

[tex]\Delta V=\frac{E}{q}=\frac{1.06\cdot 10^{-17} J}{1.60\cdot 10^{-19} C}=66.3 V[/tex]

Answer:

Oceanic crust is about 6 kilometers thick. It's composed of several layers, not including the overlying sediment. The topmost layer, about 500 meters thick, includes lavas made of basalt (that is, rock material consisting largely of feldspar and pyroxene).

Explanation:

The oceanic crust, which constitutes 55% of Earth's surface is largely made up of basalt, a type of volcanic rock. It forms from the cooling of lava and primarily includes elements such as silicon, oxygen, iron, aluminum, and magnesium. Conversely, the continental crust is mainly made up of a different kind of volcanic rock called granite.

The oceanic crust, which covers 55% of Earth's surface, is principally composed of a type of rock called basalt. Basaltic rocks are volcanic in nature, formed from the cooling of lava, and primary constituents include silicon, oxygen, iron, aluminum, and magnesium. The oceanic crust is mainly submerged under the oceans and averages about 6 kilometers in thickness.

On the contrary, the continental crust is predominantly made up of granite, a different variety of volcanic rocks, and it covers the remaining 45% of the Earth's surface. Both the oceanic and continental crusts exhibit a density approximately 3 g/cm³.

It's interesting to note that all volcanically produced rocks, including basalt and granite, are classified as igneous rocks, which are created when molten material solidifies. Additionally, the oceanic crust is among the youngest features on our planet due to the continuing seafloor spreading process which basically renews the oceanic crust over approximately 100 million years.

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The average power if both the resistance and peak emf are doubled simultaneously is 10 W.

a)

The average power is:

[tex]P_{avg}=\frac{(V_{RMS})^2}{R} \\\\[/tex]

If the resistance is doubled. The new average power is:

[tex]P_{avg}'=\frac{(V_{RMS})^2}{2R}=0.5*\frac{(V_{RMS})^2}{R} =0.5*5=2.5\ W\\\\[/tex]

b)

[tex]P_{avg}=\frac{(V_{RMS})^2}{R}= \frac{(E_o/\sqrt{2} )^2}{R} \\\\\\\\[/tex]

If the peak emf is doubled:

[tex]P_{avg}'=\frac{(2E_o/\sqrt{2} )^2}{R}=4*\frac{(E_o/\sqrt{2} )^2}{R}=4*5=20\ W[/tex]

c)

[tex]P_{avg}=\frac{(V_{RMS})^2}{R}= \frac{(E_o/\sqrt{2} )^2}{R} \\\\\\\\[/tex]

If both are doubled simultaneously:

[tex]P_{avg}'=\frac{(2E_o/\sqrt{2} )^2}{2R}=2*\frac{(E_o/\sqrt{2} )^2}{R}=2*5=10\ W[/tex]

The average power if both the resistance and peak emf are doubled simultaneously is 10 W.

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Doubling the resistance halves the average power dissipated to 2.5W. If the peak emf is doubled, the average power becomes four times, which is 20W. If both are doubled simultaneously, Pavg becomes double the initial value, which is 10W.

Given, the average power Pavg dissipated by a resistor connected to a sinusoidal emf is 5.0 W. The expression for average power Pavg is given by Pavg = (Irms)^2R.

a) If the resistance R is doubled, the average power Pavg becomes halved, which is 2.5W as per the equation Pavg = (Irms)^22R.

b) If the peak emf E0 is doubled, then the average power becomes four times, as per the equation Pavg = 4*(Irms)^2*R, which means Pavg = 20W.

c) If both resistance R and peak emf E0 are doubled simultaneously, then Pavg doubles from the initial value, because, Pavg = 2*(Irms)^2*2R giving Pavg = 10W

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Answer:

0.10 m

Explanation:

The magnetic flux through the plane is given by

[tex]\Phi = BA[/tex]

where

B is the magnetic field intensity

A is the area of enclosed by the pipe

In this problem, we know

[tex]\Phi = 7.3\cdot 10^{-3} Wb[/tex] is the flux

B = 0.90 T is the magnetic field strength

Solving the equation for A, we find the area enclosed by the pipe

[tex]A=\frac{\Phi}{B}=\frac{7.3\cdot 10^{-3} Wb}{0.90 T}=8.1\cdot 10^{-3} m^2[/tex]

We know that the area is given by

[tex]A=\pi r^2[/tex]

where r is the radius. Solving for r, we find the radius:

[tex]r=\sqrt{\frac{A}{\pi}}=\sqrt{\frac{8.1\cdot 10^{-3} m^2}{\pi}}=0.05 m[/tex]

And so the diameter is twice the radius:

[tex]d=2r=2(0.05 m)=0.10 m[/tex]

Answer:

[tex]v=\frac{d}{t}[/tex]

Explanation:

The average velocity of a moving object is given by:

[tex]v=\frac{d}{t}[/tex]

where

d is the displacement of the object

t is the time taken

In this problem, we have

d = 25 m is the displacement

t = 2 s is the time

Therefore, the average velocity of the seagull is

[tex]v=\frac{25 m}{2 s}=12.5 m/s[/tex]

Note that velocity is a vector, so it has not only a magnitude, but also a direction, which corresponds to the direction of the displacement (downward, in this example).

Answer:

B. acceleration rate

Explanation:

Answer:

B

Explanation:

Formed where mantle erupts through crust

Answer:

The Hawaiian Islands were formed where mantle erupts through crust.

Explanation:

All the Hawaiian Islands were formed by the action of volcanoes that arose from the bottom of the sea, from a source of magma (hot spot).

Hawaii's hot spot theory holds that the tectonic plate under the Pacific moves, while the hot spot stands still, creating new volcanoes. For this reason, the volcanoes of the southern half of the island of Hawaii remain active today.

The oldest islands have inactive volcanoes, but in the newest ones volcanoes still active. The island of Hawaii has five volcanoes, and one of them is one of the most active in the world, the Kīlauea.

Answer:

the salt has a greater amount of charge

Explanation:

A) Peak wavelength: 1.07 mm

The peak wavelength of the Cosmic Background Radiation can be found by using Wien's displacement law:

[tex]\lambda = \frac{b}{T}[/tex]

where

[tex]\lambda[/tex] is the peak wavelength

[tex]b=2.898\cdot 10^{-3}m\cdot K[/tex] is Wien's displacement constant

T is the absolute temperature

For the Cosmic Background Radiation,

T = 2.7 K

So the peak wavelength is

[tex]\lambda = \frac{2.898\cdot 10^{-3}m\cdot K}{2.7 K}=1.07\cdot 10^{-3} m=1.07 mm[/tex]

B) Peak frequency: [tex]2.8\cdot 10^{11}Hz[/tex]

The peak frequency can be found by using the relationship:

[tex]f=\frac{c}{\lambda}[/tex]

where

[tex]c=3.0\cdot 10^8 m/s[/tex] is the speed of light

[tex]\lambda[/tex] is the peak wavelength

Substituting numbers, we find

[tex]f=\frac{3.0\cdot 10^8 m/s}{1.07\cdot 10^{-3} m}=2.8\cdot 10^{11}Hz[/tex]

It is a celestial body constituted by ice, dust and rocks that orbit around the Sun, after having been altered by the Oort cloud; following different trajectories that can be highly eccentric elliptical (periodic trajectories), parabolic or hyperbolic.

One of the main characteristics of a comet is that it travels quite fast, on its way around the Sun and has a long tail, which always go in the opposite direction to the Sun (due to the radiation pressure of sunlight).

It is a small rocky body (smaller than a planet and larger than a meteoroid). Most of these bodies are orbiting between Mars and Jupiter in the region known as the asteroid belt; while others accumulate at Jupiter's Lagrange points, and others cross the orbits of the planets.

It is a fragment of the celestial body that moves through space, which is smaller in size to an asteroid. If it gets to enter the atmosphere of the Earth, it will start to burn by friction with it (combustion) and it will be called a meteor, while if it hits the surface, it will be called a meteorite.

Comets are loose collections of ice, dust, and small rocky particles whose orbits are usually very long and narrow

Answer:

I believe the answer is B, the paths of the planets follow an elliptical orbit around the sun.

Answer:

B. Paths of the planets follow an elliptical orbit around the sun.

Explanation:

As per Copernicus model of the universe he explained that all planets revolves around the sun in circular orbit with sun at the center of the of the path.

Now as per his theory Radius of orbit of all planets are different and the centripetal force provided by the sun for the circular path of the planets

Now as per his theory all planets must have to move with uniform speed around the sun but this was not true as we can see that the speed of all planets are different at different positions.

So here in order to correct his theory Kepler gives his law of planetary motion that all planets revolves around the sun in elliptical orbit with position of sun as one of its focus.

This path verify all the experimental results of planetary motion and hence correct answer will be

B. Paths of the planets follow an elliptical orbit around the sun.

Answer:

c)by a factor of four

Explanation:

The total energy of a simple harmonic oscillator is given by

[tex]E=\frac{1}{2}kA^2[/tex]

where

k is the spring constant of the oscillator

A is the amplitude of the motion

In this problem, the amplitude of the oscillator is doubled, so

A' = 2A

Therefore, the new total energy is

[tex]E'=\frac{1}{2}k(2A)^2=4(\frac{1}{2}kA^2)=4E[/tex]

So, the total energy increases by a factor 4.

Answer:32m/s

Explanation:

Answer:

The acceleration is  -6 m/s2

Explanation:

The equation for the speed of a body is

         V = Vo + a t

Where

Vo is the initial velocity, a is the acceleration and t is the time,

When the body stops the speed is zero

       0 = Vo + a t

        a = Vo / t

substitute values

        a = - 30/5

        a = - 6 m/s2

The negative sign indicates that acceleration opposite movement

Answer:

[tex]5\cdot 10^{-9} F[/tex]

Explanation:

The capacitance of the electrode is given by:

[tex]C=\frac{Q}{V}[/tex]

where

C is the capacitance

Q is the charge on the electrode

V is the potential difference

In this problem, we have

[tex]Q=45 nC=45\cdot 10^{-9} C[/tex]

V = 9.0 V

Substituting into the equation, we find

[tex]C=\frac{45\cdot 10^{-9}C}{9.0 V}=5\cdot 10^{-9} F[/tex] (5 nF)

Ernest Rutherford was a British physicist and chemist of New Zealand origin, who conducted a series of experiments together with Hans Geiger and Ernest Marsden; where the result led him to propose a new atomic model.

It should be noted that at that time, the "accepted" atomic model was Thomson's raisin pudding atomic model (electrons with negative charge immersed an the atom of positive charge that counteracted the negative charge of the electrons, like raisings embedded in a pudding), who discovered the electron and formerly was a professor of Rutherford.  

Now, the experiment conducted under the direction of Ruherford at the laboratories of the University of Manchester during the year 1911; was for the purpose of corroborating Thomson's atomic model. To achieve this, a thin metal sheet was bombarded with alpha particles (nuclei of helium gas).

The idea was that these alpha particles, having positive electric charge, were attracted by the atom's negative charges and repelled by the positive charges, and it was expected that they would pass through the thin sheet without hardly deviating. Then, to observe the crash site of the particle, a phosphorescent screen was placed behind and on the sides of the metal sheet.

For according to Thomson's atomic model the positive and negative charges were evenly distributed, the sphere (the atom) had to be electrically neutral, and the alpha particles would pass through the sheet without deviating.

However, the results were surprising:

As expected, most of the particles went through the sheet without deviating.

That is:

These facts could not be explained by Thomson's atomic model, so Rutherford developed another, suggesting that:

This new model could explain the proven fact in his experiments that some particles bounced in the direction opposite to the incident particles, because the electrical charge of this nucleus was positive, equal to the electrical charge of the alpha particles.

This is how Rutherford proposed a new atomic model and discovered the existence of the nucleus. However, this was not the definitive model, because on 1913 it was replaced by Bohr's.

a) zinc

The equation of the photoelectric effect is:

[tex]E=\phi + K[/tex] (1)

where

E is the energy of the incident light

[tex]\phi[/tex] is the work function

[tex]K[/tex] is the maximum kinetic energy of the emitted photoelectrons

Here the wavelength of the incident light is

[tex]\lambda=200 nm = 2\cdot 10^{-7} m[/tex]

so the energy of the light is

[tex]E=\frac{hc}{\lambda}=\frac{(6.63\cdot 10^{-34} Js)(3\cdot 10^8 m/s)}{2\cdot 10^{-7} m}=9.95\cdot 10^{-19} J[/tex]

Converting into electronvolts,

[tex]E=\frac{9.95\cdot 10^{-19}}{1.6\cdot 10^{-19} J/eV}=6.22 eV[/tex] (2)

The stopping potential is the potential needed to stop the photoelectrons with maximum kinetic energy: so, the electrical potential energy corresponding to the stopping potential (V=1.93 V) must be equal to the maximum kinetic energy of the photoelectrons,

[tex]U=q V = K[/tex]

and since the charge of the electron is

1 q = 1 e

We have

[tex]K=(1 e)(1.93 V)=1.93 eV[/tex] (3)

Combining (1), (2) and (3), we find the work function of the material:

[tex]\phi = E-K=6.22 eV-1.93 eV=4.29 eV[/tex]

So, the cathode is most likely made of zinc, which has a work function of 4.3 eV.

b) The stopping potential does not change

As we said in part A), the stopping potential is proportional to the maximum kinetic energy of the photoelectrons, K.

The intensity of light is proportional to the number of photons that hit the surface of the metal. However, the energy of these photons does not depend on the intensity, but only on the frequency of the light.

Therefore, the energy of the photons (E) does not change when the intensity of light is doubled. Also, the work function [tex]\phi[/tex] does not change: this means that the maximum kinetic energy of the photoelectrons, K, does not change, and so the stopping potential remains the same.

If the intensity of light is doubled, the stopping potential is still  1.93 V.

The term photoelectric effect refers to the fact that electrons are emitted from the surface of a metal when it is irradiated with light of the appropriate frequency.

Now;

Kinetic energy = Energy of photon - work function

Energy of the photon = 6.6 * 10^-34 * 3 * 10^8/200 * 10^-9

= 9.9 * 10^-19 J

For the stopping potential or kinetic energy;

1 ev = 1.6 * 10^-19 J

1.93 eV = 1.93eV *  1.6 * 10^-19 J/1 ev = 3.1 * 10^-19 J

Work function of the metal = 9.9 * 10^-19 J - 3.1 * 10^-19 J

= 6.8 * 10^-19 J or 4.25 eV

The metal is zinc

We know that the stopping potential is independent of the light intensity hence if the intensity of light is doubled, the stopping potential is still  1.93 V.

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the hot chocolate in the large pot has more therma energy than the hot chocolate in the mug

Answer:

The hot chocolate in the large pot has more thermal energy than the hot chocolate in the mug.

The hot chocolate in the large pot has more average kinetic energy than the hot chocolate in the mug.

Explanation:

Thermal energy is defined as the energy posses by an object because of kinetic energy of atoms present in it.

These atoms moves in a great pace or more rapidly when heat is transferred to them hence more the heat more will be the kinetic energy of the material.

In this case, hot chocolate is in large pot and thus has more temperature than the other mug.

Which explains it has more kinetic energy as well as more thermal energy.

1. 5765 mol

First of all, let's calculate the volume of the room (which corresponds to the volume of the gas):

[tex]V=7.00 m\cdot 8.00 m \cdot 2.50 m=140 m^3[/tex]

We also know the following data about the gas:

[tex]T=22.0^\circ +273 =295 K[/tex] is the temperature

[tex]p=1.00atm = 1.01\cdot 10^5 Pa[/tex] is the pressure

Then we can use the ideal gas law

[tex]pV=nRT[/tex]

with R being the gas constant

to find the number of moles of the gas:

[tex]n=\frac{pV}{RT}=\frac{(1.01\cdot 10^5 Pa)(140 m^3)}{(8.314 J/mol K)(295 K)}=5765 mol[/tex]

2. 184.5 kg

The molar mass of oxygen is

[tex]M_m = 32.0 g/mol[/tex]

this corresponds to the mass of 1 mol of oxygen.

In this problem, the number of moles is

n = 5765 mol

So the total mass of these n moles of oxygen will be:

[tex]m=n M_m = (5765 mol)(32.0 g/mol)=1.845\cdot 10^5 g=184.5 kg[/tex]

The Soviet Union's Sputnik 1, it was launched October 4th 1957.

sodium is found in group one element, but flourine members of halogens . oxygen found in group six element ,but hydrogen found in group 1( according to periodic table)

Sodium and fluorine form ionic compounds based on their electron transfer, while oxygen and hydrogen bond covalently to create water, reflecting their differences in electronegativity and bonding mechanisms.

Comparing Sodium and Fluorine; Oxygen and Hydrogen

Sodium and fluorine differ in their electron configurations and bonding, resulting in ionic compounds, whereas oxygen and hydrogen can combine to form water through covalent bonding, demonstrating differences in electronegativity and molecular structure.

sodium (Na) is a metal with one valence electron which it readily loses to become a positively charged ion (Na+). Fluorine (F), on the other hand, is a non-metal with seven valence electrons and gains an electron to become a negatively charged ion (F-). When they bond, the resulting compound is ionic due to the high electronegativity difference. Oxygen (O2) and hydrogen (H2) both exist as diatomic molecules, but their contrast lies in the fact that oxygen is highly electronegative while hydrogen has a lower electronegativity, leading to a polar covalent bond when they form water (H2O).

while both pairs form stable compounds, the nature and type of bonding that occurs between sodium and fluorine, and oxygen and hydrogen, are fundamentally different due to their contrasting properties.

1. 686 nm

The lowest photon energy is

[tex]E=1.8 eV[/tex]

Let's convert this energy into Joules first

[tex]E=(1.8 eV)(1.6\cdot 10^{-19} J/eV)=2.9\cdot 10^{-19} J[/tex]

The energy of the photon is given by

[tex]E=\frac{hc}{\lambda}[/tex]

where

h is the Planck constant

c is the speed of light

[tex]\lambda[/tex] is the wavelength

Re-arranging the equation for [tex]\lambda[/tex], we find the maximum wavelength of the photon that can cause a transition:

[tex]\lambda=\frac{hc}{E}=\frac{(6.63\cdot 10^{-34}Js)(3\cdot 10^8 m/s)}{2.9\cdot 10^{-19} J}=6.86\cdot 10^{-7}m=686 nm[/tex]

2. Visible light

The photon of this light is in the visible light part of the spectrum.

In fact, the range of wavelengths of the visible part of the spectrum is

[380 nm - 750 nm]

In particular, we have that the wavelengths in the range

[640 nm - 750 nm]

corresponds to the red light part of the spectrum: since 686 nm falls withing this range, this photon is a red light photon.

The maximum wavelength of electromagnetic radiation that can cause a transition in rhodopsin is approximately 389 nm, which lies in the visible light part of the spectrum.

The maximum wavelength of electromagnetic radiation that can cause a transition in rhodopsin can be calculated using the equation E = hc/λ, where E is the energy of the photon, h is Planck's constant, c is the speed of light, and λ is the wavelength of the radiation. Rearranging the equation to solve for λ, we have λ = hc/E. Plugging in the given values, we get λ = (6.626 x 10^-34 J · s x 3 x 10^8 m/s)/(1.8 x 1.602 x 10^-19 J) ≈ 389 nm.

This wavelength lies in the visible light part of the spectrum. Visible light ranges from approximately 400 to 700 nm, with shorter wavelengths corresponding to violet light and longer wavelengths corresponding to red light.

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Nuclear fission is the reaction in which the nucleus of a heavy atom, when bombarded with neutrons (or when capturing an incident neutron), becomes unstable and divides into two or more nuclei of lighter atoms, giving rise to a situation of greater stability. In this process that takes place in the atomic nucleus, neutrons, gamma rays and large amounts of energy are emitted.

In addition, several neutrons are produced that affect other fissile nuclei,and trigger more fission reactions that in turn generate more neutrons. Effect known as chain reaction.

Answer:

A. It passes wthout any deviation

Explanation:

In real lenses the light does not go straight through, there is a refraction. But we can assume that that it passes without any deviation because the center of a lens is comparatively flat that the other points of the lens.

Answer:

A.  It passes without any deviation.

Explanation:

For making ray diagram, following rules are followed:

Thus, the correct option is A.

Using the given equation you get:

E = 1.99x10^-25 / 9.0x10^-6

Divide 1.99 by 9.0: 1.99/9.0 = 0.22

For the scientific notation, when dividing subtract the two exponents:

25 -6 = 19

So you now have 0.22 x 10^-19

Now you need to change the 0.22 to be in scientific notation form:

2.2 x 10^-20

The answer is B.

Resonance is a phenomenon that occurs when a body capable of vibrating is subjected to the action of a periodic force, whose frequency of vibration approaches the characteristic frequency of vibration (called resonance frequence) of said body. This is due a relatively small force applied in a repeated form, causing the amplitude of the oscillating system to become very large.

In other words, for the specific case of sound waves, this phenomenon occurs when the frequency of the  wave that is external to the system or body coincides with the resonance frequency (characteristic frequency that reaches the maximum degree of oscillation) of this system or body.

In these circumstances the body vibrates, progressively increasing the amplitude of movement after each successive actions of the force. However, this effect can be destructive in some rigid materials.

Answer:

D. The current in the battery and in each resistor is the same

Explanation:

In a series circuit, all the components of the circuit are connected in the same branch of the circuit - this means that the current flowing through each component is the same. Therefore, the current in the battery is equal to the current flowing through each resistor.

The total resistance of a series of n resistors is given by the sum of the individual resistances:

[tex]R=R_1+R_2+...+R_n[/tex]

On the contrary, when the components are connected in parallel to the battery, then each of them has the same voltage of the battery, but not the same current.

Definition

Acceleration is the term used to describe an object that is either speeding up or slowing down.

Explanation

Based on the given answer choices, answer choices A, C, and D does not describe an object either gaining speed or losing speed; however, object B states this. For this reason, answer choice B is the correct answer.

Answer

b. ac car slowing down on a sharp curve

Final answer:

Acceleration is any change in the velocity of an object, which includes speeding up, slowing down, or changing direction. The example of a car slowing down on a sharp curve is a clear illustration of acceleration.

Explanation:

The question: Which is an example of acceleration? involves understanding the concept of acceleration in physics. Acceleration refers to any change in the velocity of an object, which includes speeding up, slowing down, or changing direction. Therefore, the correct answer is b. a car slowing down on a sharp curve. This example perfectly illustrates acceleration because the car is changing its speed (slowing down) as it moves around the curve, which is a change in velocity. The other options, such as a pickup driving a constant distance in a specific time, an airplane traveling at a constant speed, or an 18 wheeler driving west at a constant speed, do not necessarily imply a change in speed or direction, and thus, do not serve as clear examples of acceleration.