Question

You ask a friend to help you record a YouTube video. Your inertia is 70 kg, and you plan to step off the roof of a small building just at the instant your friend throws a baseball in your general direction. Your goal is to catch the ball on the way down, land on a trampoline, then relax and bounce vertically until you eventually stop. The figure shows the initial setup with relevant dimensions given. Ignore air drag, and assume constant gravitational acceleration equal to 9.8 m/s

Which choice best represents the angle to the horizontal at which your friend should throw the baseball?

A.

32



B.

39



C.

48



D.

58



E.

65



If 700 J of mechanical energy is converted to some form of internal energy each time you bounce on the trampoline, how many bounces are required for you to come to rest?

A.

3

B.

4

C.

5

D.

7

E.

None of these

Of 71 。 -ZOOM ber 6.3 m 1.5 m 3.0 m 5:06 12/2/

Answer 1

H = 6.3 m: h = 1.5 m so, angle of projection is tan theta = (H - h)/3 = (6.3 - 1.5)/3 implies theta = 57.99 almostequalto 58 so, option (D) is correct mass of person, m = 70 kg energy dissipated in each jump thatis delta E = 700 J so, number of bounces are n = mg (H - h)/delta E = 70 times 9.81 (6.3 - 1.5)/700 or, n = 4.7088 almostequalto 5 so, option (D) is correct