40 POINTS CORRECT ANSWER
Why does hot air rise and cold air sink?

A ) Cold air has more kinetic energy than hot air.

B ) Hot air has more potential energy than cold air.

C ) Cold air is more dense than hot air.

D ) Hot air is more dense than cold air.

Answer:

When there is an outlier in the data set, the dot plot or histogram will be skewed. In a skewed representation, the mean is pulled up or down toward the tail of the data. Therefore, skewed data affects the mean more than the median.

Explanation:

The dot plot or histogram will be skewed.

The Gold foil experiment by Rutherford discovered the atomic nucleus and protons. Protons are positively charged particles and will pass to the negative end. Hence, the alpha particles pass through electron cloud.

Gold foil experiment conducted by Rutherford was leading to the discovery  of positively charged particles later called protons and the core of the atom called the nucleus in which protons are located.

Rutherford forwarded an atomic model known as nuclear model. In his experiment, the alpha particles was deviating due to repulsion  from the the metal foil and they passed through the negative charged electron cloud.

Rutherford later called this positively charged particles as protons and he found that they are located in the inner core of the atom called nucleus. Therefore, option C is correct.

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Answer: the boat is more dense in salt water

Explanation:

Answer:

3 × 10⁴

Explanation:

We are given two numbers, [tex]n_1=9\times 10^{-5}[/tex] and [tex]n_2=3\times 10^{-9}[/tex]

We have to divide n₁ by n₂. We know that,

[tex]\dfrac{10^n}{10^m}=10^{n-m}[/tex]

Here, n = -5 and m = -9

So on dividing we get :

[tex]\dfrac{9\times 10^{-5}}{3\times 10^{-9}}=3\times 10^{-5+9}=3\times 10^4[/tex]

Hence, on dividing n₁ by n₂ obtained number is 3 × 10⁴.

The guy  below me is wrong the correct answer is intrusive igneous rock

Answer:

The moving car transfers Kinetic Energy to the parked car

Explanation:

Options are not supplied here but I have previously answered this question in a test and these options were supplied.

A) The moving car transfers kinetic energy to the parked car.

B) Kinetic energy in the moving car disappears.

C) Kinetic energy in the parked car is created.

D) The parked car transfers kinetic energy to the moving car.

A) This option provides us with the true outcome, the moving car transfers Kinetic energy to the parked car. This is in agreement with the law of conservation of energy. A transference of energy is the outcome of this event.

B) Kinetic energy cannot disappear, this is because according to the law of conservation of energy, energy can neither be created nor destroyed.

If energy disappears, this would imply that energy is destroyed which is not agreeable.

C) Kinetic energy in the parked car is created... Just like the option B above, and according to the above stated law, energy can neither be created nor destroyed. It is also not agreeable here that energy is created.

D) Energy can be transferred but, "a parked car indicates that the car only has potential energy" and as such cannot transfer kinetic energy to the moving car since it does not possess kinetic energy.

The acceleration of air when you sneeze, accelerating from rest to approximately 44.44 m/s (160 km/hr) in about 0.55 seconds, is 80.8 m/s².

When you sneeze, the air in your lungs accelerates from rest to approximately 160 km/hr, which is equal to ≈ 44.44 m/s (since 1 km/hr is equivalent to ≈ 0.27778 m/s). To find the acceleration of the air, we use the formula:

a = (v - u) / t

Where a is acceleration, v is final velocity, u is initial velocity (which is 0 m/s in this case, as the air starts from rest), and t is the time over which acceleration occurs. Plugging in the values gives us:

a = (44.44 m/s - 0 m/s) / 0.55 s = 80.8 m/s²

Therefore, the acceleration of the air in m/s² when you sneeze is 80.8 m/s².

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Answer: B. magnetic field

Explanation:

Wind blows when there is difference in air pressure i.e. in the area having pressure gradient, wind blows from high pressure area to low pressure area. Force of friction slows the speed of the wind. Thus it is responsible for motion of air. Coriolis effect causes the circular motion of the air. The Coriolis effect changes the direction of the wind.

Thus, from the given options, only the magnetic field does not influence the wind. Magnetic field effects the charged particles or magnetic materials not the wind.  

The acceleration of an object is not inversely proportional to the net force; it is directly proportional to the net force and inversely proportional to the mass of the object.

The statement that the acceleration of an object is inversely proportional to the net force acting on it is false. According to Newton's second law of motion, the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This law is often expressed with the formula a = F/m, where a is acceleration, F is the net force, and m is the mass of the object.

To control the momentum your car carries in a potential crash, get your car installed with good quality air bags.

Momentum is defined as the product of mass and velocity.

Given is to find how to control the momentum your car carries in a potential crash.

The one thing you can do is to get your car installed with good quality air bags. Air bags reduce the momentum of the body by a substantial level.

Therefore, to control the momentum your car carries in a potential crash, get your car installed with good quality air bags.

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To calculate the mass of water that evaporates, we apply energy conservation between the heated iron block and the water. Heat transfers from the iron to the water until the water boils and some evaporates. Specific heat capacities and latent heat values are needed for a numerical solution.

To calculate the mass of water that boiled off when a 5kg block of iron is heated to 800℃ and placed in a tub containing 2 liters of water at 15℃, we apply the concept of conservation of energy. The heat lost by the iron block will be equal to the heat gained by the water, which will result in water reaching its boiling point and some of it evaporating. The specific heat capacity of water, the heat of vaporization of water, and the specific heat capacity of iron are crucial to these calculations.

We can denote the mass of water that evaporates as m, and calculate the heat required to raise the temperature of the remaining water from 15℃ to 100℃ and convert the m grams of water at 100℃ into steam. However, we need additional data such as the specific heat capacities and the latent heat of vaporization for water to provide a concrete answer. Without the specific values, we can only describe the methodology.

Final answer:

To find the velocity of a quarter dropped from a tower after 10 seconds, we use the formula for velocity in free fall, resulting in a final velocity of 100 m/s.

Explanation:

The question is about determining the velocity of a quarter dropped from a tower after 10 seconds. To solve this, we use the formula for velocity in free fall, v = gt, where g is the acceleration due to gravity (approximated as 10 m/s²) and t is the time in seconds. In this case, after 10 seconds, the velocity can be calculated as follows:

g = 10 m/s² (approximation of the acceleration due to gravity)

t = 10 seconds

Substitute the values into the formula: v = gt = 10 m/s² × 10 s = 100 m/s.

Therefore, the velocity of the quarter after falling for 10 seconds is 100 m/s.

Answer;

B. Bourdon gage—indicate steam pressure in a furnace

Explanation;

-Bourdon gauge is an instrument for measuring the pressure of gases or liquids, consisting of a semicircular or coiled, flexible metal tube attached to a gauge that records the degree to which the tube is straightened by the pressure of the gas or liquid inside.

-The Bourdon pressure gauge operates on the principle that, when pressurized, a flattened tube tends to straighten or regain its circular form in cross-section.

-When a gauge is pressurized, the Bourdon creates the dial tip travel to enable pressure measurement. The higher the pressure requirement of the application, the stiffer the Bourdon tube needs to be, which means Bourdon wall thickness and diameter are key considerations for enabling the required tip travel to traverse the necessary movement and, thus, facilitate pressure measurement accuracy.

Final answer:

Temperature affects the evaporation rate of water as higher temperatures provide more energy for evaporation. This phenomenon is exemplified by perspiration from the skin which requires more heat input than the latent heat of vaporization at 100 °C, showcasing an effective cooling mechanism in hot weather.

Explanation:

Temperature affects the evaporation rate of water. The higher the temperature, the faster the water molecules move, and the more likely they are to escape and evaporate. This is because the kinetic energy of water molecules increases with temperature, providing more energy for evaporation.

For example, at body temperature, perspiration from the skin requires more heat input than the latent heat of vaporization at 100 °C. This heat comes from the skin, resulting in an effective cooling mechanism in hot weather.

However, it's important to note that temperature is not the only factor that affects evaporation. Other factors like humidity and surface area of contact between air and water also play a role.

Final answer:

The problem is a high school level physics kinematics question. It requires setting up two kinematic equations representing the motion of both cyclists and solving for the time when the second cyclist catches up.

Explanation:

The student is asking about the time it will take for a second cyclist to catch up to the leader in a race, given the leader's constant velocity and the second-place cyclist's velocity and acceleration. This is a physics problem involving kinematics, specifically equations of motion.

To solve this problem, you need to set the distances traveled by both cyclists equal to each other and solve for time. Since the first cyclist is moving at a constant velocity, the distance he travels can be represented by d1 = v1*t, where d1 is the distance, v1 is the velocity, and t is time. For the second cyclist with acceleration, you can use the formula d2 = v2*t + 0.5*a*t2, where d2 is the distance, v2 is the initial velocity, a is the acceleration, and t is the time.

Since the second cyclist has to cover an additional 11.4 m to catch up, we modify the equation for d2 to d2 = v2*t + 0.5*a*t2 + 11.4. Now you set d1 equal to d2 and solve for t using quadratic formula or other methods to find when both distances are the same, indicating the second cyclist has caught up.

Final answer:

The density of a marble block with a mass of 824 g and volume of 236 cm³ is calculated by dividing mass by volume, resulting in approximately 3.4915 g/cm³.

Explanation:

The density of an object can be calculated using the formula density = mass/volume. In this case, we are given that the mass of the block of marble is 824 grams and it occupies a volume of 236 cm³. To find the density in units of grams per cubic centimeter (g/cm³), we simply divide the mass by the volume.
Using the formula:

Density = mass / volume

Density = 824 g / 236 cm³

Density = 3.4915 g/cm³ (rounded to four decimal places)

Therefore, the density of the marble block is approximately 3.4915 g/cm³.

The critical value of the coefficient of static friction (μs) is calculated by dividing the maximum static friction force by the normal force. This critical value represents the point at which a person is unable to exert enough force to overcome the maximum static friction and initiate movement of the object.

To calculate the critical value of

, we need to understand the relationship between the maximum static frictional force (fs(max)) and the normal force (N). The maximum static friction can be represented as

fs(max) =  N.

This means that static friction increases to match the applied force until it reaches a maximum value, beyond which the object will move. In the provided scenario, the maximum static frictional force required to move the crate is 440 N, with a given normal force due to gravity of 980 N. The coefficient of static friction was given as 0.45. From this, we have the equation 440 N = 0.45 * 980 N.

The critical value  occurs when a person is unable to exert a force greater than the maximum force of static friction. If, for example, a person can only exert a force less than 440 N, the critical coefficient  would have to be such that the maximum static friction force (N) equals the maximum force the person can exert, thus preventing the initiation of motion.

To determine this critical value, we would set the person's maximum possible force to equal fs(max), solving for

as follows: fs(max) =  N. If the maximum possible force exerted by the person is less than 440 N, say 400 N, the critical

would be 400 N / 980 N, which yields a critical value greater than the original  of 0.45.

Final answer:

The universe is vast and complex with billions of galaxies and stars. It displays an astonishing degree of order with regular laws governing planetary motion and precise arrangements in living organisms. Dark matter, a mysterious form of matter that does not emit light, is also present in the universe.

Explanation:

The major characteristics of the universe in terms of time, distance, and organization are as follows:

The universe is vast and complex, consisting of approximately 10¹¹ galaxies in the observable part. An average galaxy contains more than 10¹¹ stars, with our Milky Way galaxy being larger than average.

The universe displays an astonishing degree of order, with regular laws governing the motion of planets around the sun and the precise arrangement of animals' parts to serve their purposes.

There is evidence of a large amount of additional matter in galaxies called dark matter, which does not produce light and is still being studied.

These characteristics provide insights into the vastness, orderliness, and complexity of our universe.

C. +Q, +W

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Final answer:

The correct signs of heat and work when a balloon expands due to heating are +Q for heat absorbed by the gas and -W for work done by the gas on the surroundings, making the correct option A. +Q, -W.

Explanation:

When the gas in a balloon is heated, it expands and does work on its surroundings. According to thermodynamic conventions, when a system (like the gas in a balloon) does work on its surroundings, this work is assigned a negative sign (W < 0). Simultaneously, as the gas is heated, it absorbs heat (Q > 0), which is indicated by a positive sign. Therefore, the correct signs for heat and work for the expanding balloon are +Q for heat absorbed and -W for work done by the gas on its surroundings. The answer that correctly represents these signs is A. +Q, -W.

The acceleration of a car moving along a straight-line path that increases its speed from zero to 100 km/hr in 10 seconds would be 2.77 m /s² .

There are three equations of motion given by  Newton

v = u + at

S = ut + 1/2×a×t²

v² - u² = 2×a×s

As given in the problem, we have to find  the acceleration of a car moving along a straight-line path that increases its speed from zero to 100 km/hr in 10 seconds,

100 km / hr = 100 × 1000 / 3600

                   = 27.77 m / s

By using the first equation of the motion,

v = u + at

27.77 = 0 + 10a

a = 2.77 m /s²

Thus, the acceleration would be 2.77 m /s².

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