Physics

A skier is skiing down a slope on the mountain.Is the mechanical energy conserved? Why or why not?The mechanical energy isn't conserved. Some energy is lost to gravity.The mechanical energy isn't conserved. Some energy is lost to friction.Mechanical energy is always conserved.The mechanical energy is conserved. There is as much KE at the end as there was PE at the beginning.
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Why do optical astronomers often put their telescopes at the tops of mountains, whereas radio astronomers sometimes put their telescopes in deep valleys?
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Imagine holding a basketball in both hands, throwing it straight up as high as you can, and then catching it when it falls. At which points in time does a zero net force act on the ball? Ignore air resistance.(A) When you hold the ball still in your hands after catching it(B) Just after the ball first leaves your hands.(C) At the instant the ball reaches its highest point.(D) At the instant the falling ball hits your hands.(E) When you hold the ball still in your hands before it is thrown.
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A steel wire in a piano has a length of 0.600 m and a mass of 5.200 103 kg. To what tension must this wire be stretched so that the fundamental vibration corresponds to middle C (fC = 261.6 Hz on the chromatic musical scale)?
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A 10,844.0 kg truck is initially at rest. The truck then accelerates across a level road and reaches a constant speed. It takes the truck 25.4 seconds to reach its final speed. At this speed, the truck has 41,505.4 joules of kinetic energy. How much power did the truck require to accelerate the truck in this time? Round your answer to the tenths place.
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A light beam in glass (n = 1.5) reaches an air-glass interface, at an angle of 60 degrees from the surface. What is the angle of the refracted light beam from the normal in air?Note: sin(30) = 0.5, sin(45) = 0.71, sin(60) = 0.87 (all angles are in degrees)
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An electric motor exerts a constant torque of 10 Nm on a grindstone mounted on its shaft. The moment of inertia of the grindstone is I = 2.0 kgm2 . The system starts from rest. A. Determine the angular acceleration of the shaft when this torque is applied. B. Determine the kinetic energy of the shaft after 8 seconds of operation. C. Determine the work done by the motor in this time. D. Determine the average power delivered by the motor over this time interval
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u are holding the axle of a bicycle wheel with radius30 cm and mass 1.05 kg. You get the wheel spinning at arate of 77 rpm and then stop it by pressing the tire againstthe pavement. You notice that it takes 1.37 s for the wheelto come to a complete stop. What is the angular accelerationof the wheel
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A spring on Earth has a 0.500 kg mass suspended from one end and the mass is displaced by 0.3 m. What will the displacement of the same mass on the same spring be on the Moon, where the acceleration due to gravity is one sixth that of Earth? Show your work.
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Earth's atmosphere is constantly bombarded by cosmic ray protons that originate somewhere in space. If the protons all passed through the atmosphere, assume that each square meter of Earth's surface would intercept protons at the average rate of 1110 protons per second. What would be the electric current intercepted by the total surface area of the planet?
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A shallow slope on a phase-change graph indicates _____.A. a little temperature increase for a lot of heatB. a phase changeC. a large change in kinetic energy of the moleculesD. a high latent heat
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A dock worker applies a constant horizontal force of 80.5 N to a block of ice on a smooth horizontal floor. The frictional force is negligible.The block starts from rest and moves a distance 13.0 m in a time 4.50 s.(a)What is the mass of the block of ice?----- I found this to be 56.9kg and got it right.(b)If the worker stops pushing at the end of 4.50 s, how far does the block move in the next 4.20s ? -
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Three resistors are connected into the section of the circuit described by the diagram. Then the wire is cut at point x, and the two cut ends of the wire are separated. Through which of the three resistors, if any, does current still flow?A. None of the resistorsB. All three resistorsC. R1 onlyD. R1 and R2 only
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How much excess charge must be placed on a copper sphere 25.0 cm in diameter so that the potential of its center, relative to infinity, is 1.50 kV?
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A toy helicopter is flying in a straight line at a constant speed of 4.5 m/s. If a projectile is launched vertically with an initial speed of v0 = 28 m/s, what horizontal distance d should the helicopter be from the launch site S if the projectile is to be traveling downward when it strikes the helicopter? Assume that the projectile travels only in the vertical direction.
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Why are airbags, helmets, and other safety devices important? Physics
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In The Funeral of St. Bonaventure, Francisco de Zurbarn used the principle of __________ to create emphasis and focal point.
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A car is initially traveling west at 25 mph, and makes a turn north. As the car finishes the turn, its velocity is 20 mph north. It takes 3.5 seconds to complete the turn. What is the average acceleration of the car while it is turning, in mph/s?a. 0 -7.11+5.7.b. 7.1-5.73.c. 571-7.13.d. -5.7i+71.
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Vector A is 3.00 units in length and points along the positive x-axis. Vector B is 4.00 units in length and points along the negative y-axis. Use graphical methods to find the magnitude and direction of the following vectors:
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What mass of a material with density rho is required to make a hollow spherical shell having inner radius r1 and outer radius r2? (Use any variable or symbol stated above as necessary.)
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The vertical deflecting plates of a typical classroom are a pair of parallel square metal plates carrying equal but opposite charges. Potential difference between the plates is 25.0V; typical dimensions are about 3.8cm on a side with a separation of about 4.6mm. Under these conditions, how much charge is on each plate? How stron is the electric field between the plates? I fan electron is ejected from the negative plates, how fast is it moving when it reaches the postive plate?
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A water break at the entrance to a harbor consists of a rock barrier with a 50.0-m-wide opening. Ocean waves of 20.0-m wavelength approach the opening straight on. At what angles to the incident direction are the boats inside the harbor most protected against wave action?
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Which of the following are molecules?
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The nucleus of a plutonium-239 atom contains 94 protons. Assume that the nucleus is a sphere with radius 6.64 fm and with the charge of the protons uniformly spread through the sphere. At the surface of the nucleus, what are the (a) magnitude and (b) direction (radially inward or outward) of the electric field produced by the protons
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