In order to increase the amount of exercise in her daily routine, Tara decides to walk up the three flights of stairs to her car instead of taking the elevator. Each of the ste she takes are 18.0 cm high, and there are 12 steps per flight. (a) If Tara has a mass of 52.5 kg, what is the change in the gravitational potential energy of the Tara-Earth system (in J) when she reaches her car? (b) If the human body burns 1.5 Calories (6.28 x 10° J) for each ten steps climbed, how much energy (in J) has Tara burned during her climb? (c) How does the energy she burned compare to the change in the gravitational potential energy of the system? Epurned %3D Δυ

Someone drops a 70 – g pebble off of a docked cruise ship, 50.0 m from the water line. A person on a dock 5.0 m from the water line holds out a net to catch the pebble. (a) How much work is done on the pebble by gravity during the drop? (b) What is the change in the gravitational potential energy during the drop? If the gravitational potential energy is zero at the water line, what is the gravitational potential energy (c) when the pebble is dropped? (d) When it reaches the net? What if the gravitational potential energy was 40.0 Joules at water level? (e) Find the answers to the same questions in (c) and (d). |

A 230 g block is dropped onto a relaxed vertical spring that has a spring constant of k = 1.3 N/cm (see the figure). The block becomes attached to the spring and compresses the spring 14 cm before momentarily stopping. While the spring is being compressed, what work is done on the block by (a) the gravitational force on it and (b) the spring force? (c) What is the speed of the block just before it hits the spring? (Assume that friction is negligible.) (d) If the speed at impact is doubled, what is the maximum compression of the spring? (a) Number (b) Number (d) Number 3155 - 1.274 (c) Number 2.88 9 Units Units Units J J m/s Units m/s

You drop a 2.60 kg book to a friend who stands on the ground at distance D = 12.0 m below. If your friend's outstretched hands are at distance d = 1.50 m above the ground (see the figure), (a) how much work Wg does the gravitational force do on the book as it drops to her hands? (b) What is the change AU in the gravitational potential energy of the book-Earth system during the drop? If the gravitational potential energy U of that system is taken to be zero at ground level, what is U (c) when the book is released and (d) when it reaches her hands? Now take U to be 100 J at ground level and again find (e) Wg, (f) AU, (g) U at the release point, and (h) U at her hands. (a) Number i Units (b) Number i Units (c) Number i Units (d) Number i Units (e) Number i Units (f) Number i Units (g) Number i Units (h) Number i Units > > > > > > >