Consider an object launched vertically upward. Neglect air resistance. The maxim

Question

Consider an object launched vertically upward. Neglect air resistance. The maximum height reachcd by the object is 25.0 m. By using energy conservation, calculate (a) the initial velocity of the object, (b) the speed of the object when it is at a height h = 12.0 m, and (c) the height where the speed of the object is 10.0 m/s. 2. A 75.0-kg swimmer jumps into the old swimming hole from a diving board 3.75 m above the water, (a) Use energy conserv ation to find his speed just he hits the water if he just holds his nose and drops in. (b) Use energy conserv ation to find his speed just he hits the water if he bravely jumps straight up (but just beyond the board!) at 2 m/s. (c) In case (b), how large must be the resistance force exerted by the water in order for the swimmer to come to rest at 2.0 m under the surface.

Explanation / Answer

2)

conserving energy

mgh = 0.5mv^2

V = sqrt ( 2gh)

v = 8.57m/s

b)

mhg + 0.5m2^2 = 0.5mV^2

V= sqrt ( 4 +2gh)

V = 8.8m/sec

c)

mg2 +0.5m(8.8)^2 -F x 2 =0

F = 2188.125 N

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