Work, power & energy Questions and Answers

A flower vase sits on a high shelf. If the vase were to fall off the shelf, which of the following statements would be true as it falls? Choose all that apply. A. The potential energy of the vase would decrease. B. The total energy of the vase would remain the sam C. The total energy of the vase would increase. D. The potential energy of the vase would remain the same. E. The kinetic energy of the vase would remain the same. F. The kinetic energy of the vase would decrease. G. The kinetic energy of the vase would increase. H. The total energy of the vase would decrease. I. The potential energy of the vase would increase.

The law of conservation of energy states that - A. Potential energy is always greater than kinetic energy. B. The total energy of a system is constant. C. Potential and kinetic energy are always equal to each other. D. Potential energy is always less than kinetic energy.

Your class is asked to plan an investigation to demonstrate the conservation of energy. Two groups each wrote their own plan. We will use a battery powered toy car to demonstrate conservation of energy. It will roll across a flat table three times. Keeping the distance constant, we will time it with a stopwatch. We will calculate its average speed, and from there, determine how much energy it had. We will roll a ball down a ramp. Photogates will measure the ball's speed at 10 places along the ramp. We will use a ruler to measure the ball's height at those same 10 places. Then we will graph the kinetic energy vs. displacement and the potential energy vs. displacement to compare them. Which group best completed their objective, and why?

James uses a rope to lift supplies weighing 400 N to his tree-house. It takes 5 seconds to lift them to a height of 2 meters. Calculate how much work he did. A. 50 J B. 200 J C. 5 J D. 800 J E. 400 J

Physics students launch a ball straight up and observe the ball as it returns to the same height. They determine the ball has 80 J of kinetic energy when launched, but has less than 80 J of kinetic energy when it returns. Which statement most likely accounts for the difference in kinetic energy? A. The ball has a negative velocity during the fall, causing the final kinetic energy to be less than the initial kinetic energy. B. The ball encounters air resistance, causing the magnitude of the final velocity to be less than the initial velocity. C. The ball cannot lose kinetic energy, there must be an error in the calculations. D. The ball encounters air resistance, causing the final mass to be less than the initial mass.

A large cruise ship of mass 6.00 x 107 kg has a speed of 12.8 m/s at some instant. (a) What is the ship's kinetic energy at this time? (b) How much work is required to stop it? (Give the work done on the ship. Include the sign of the value in your answer.) (c) What is the magnitude of the constant force required to stop it as it undergoes a displacement of 3.80 km?

A pitcher claims he can throw a 0.148-kg baseball with as much momentum as a 2.02-g bullet moving with a speed of 1.50 x 10³ m/s. (a) What must the baseball's speed be if the pitcher's claim is valid? (b) Which has greater kinetic energy, the ball or the bullet? The ball has greater kinetic energy. Both have the same kinetic energy. The bullet has greater kinetic energy.

A projectile of mass m is fired horizontally with an initial speed of vo from a height of h above a flat, desert surface. Neglecting air friction, at the instant before the projectile hits the ground, find the following in terms of m, vo, h, and g. (a) the work done by the force of gravity on the projectile W = mgh (b) the change in kinetic energy of the projectile since it was fired AKE = mgh (c) the final kinetic energy of the projectile KE= 1/2mv²0+ mgh X (d) Are any of the answers changed if the initial angle is changed? Yes No