On the y-axis (Free Fall, thus FG = W =mg), a 9 kg object is released from 15 m. a. Calculate the work done by the gravitational force when it reached a final position of 8m.

7. A student in a lab exerts a 25 N force to pull a block a distance of 48 cm. If a total of 11 J of work is done, the angle between the force and the displacement is a. 89° b. 66° d. 24° e. none of the above c. 61° 8. A 102-g sparrow flying at 12.3 m/s wishes to have equal kinetic and gravitational potential energies. The height that will accomplish this is a. 0.315 m b. 0.628 m d. 1.13 m e. 7.72 m c. 0.787 m 9. Earth's mass is 5.98 x 1024 kg. Calculate the value of g at a point 4.8 x 105 km from the centre of Earth. a. 9.8 × 102 N/kg b. 8.3 x 10' N/kg C. 1.7 × 103 N/kg d. 1.7 x 10³ N/kg e. 9.8 × 105 N/kg 10. A piece of paper becomes electrically charged when a charged rod of plastic is placed close to it. This is referred to as a. charging by a conductor b. charging by induction c. charging by an insulator A P d. charging by contact e. charging by electricity 20 cm Ꭰ T 20 cm 11. Four charged spheres, A, D, P, and T are arranged as shown below. Sphere A has a charge of +4.5 × 10*C,…

You drop a 2.50 kg book to a friend who stands on the ground at distance D-13.0 m below. If your friend's outstretched hands are at distance d-1.60 m above the ground (see the figure), (a) how much work W, 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) W. (f) AU, (g) U at the release point, and (h) U at her hands. 10000 El

15. A particle is subject to a force F, that varies with posi- W tion as shown in Figure P7.15. Find the work done by the force on the particle as it moves (a) from x = 0 to 5.00 m, (b) from x = 5.00 m to x = 10.0 m, and (c) from x= 10.0 m to x = 15.0 m. (d) What is the total work done by the force over the distance x = 0 to x = 15.0 m? x= F, (N) 3 2 1 0 x (m) 2 4 6 8 10 12 14 16 Figure P7.15 Problems 15 and 34.