1. A 46-kg pole vaulter running at 12 m/s vaults over the bar. Her speed when sh

Question

1. A 46-kg pole vaulter running at 12 m/s vaults over the bar. Her speed when she is above the is bar is 1.3 m/s. Neglect air resistance, as well as any energy absorbed by the pole, and determine her altitude as she crosses the bar.

________m (answer)

2. A 2.1x10^3-kg car starts from rest at the top of 5.3 m-long driveway that is inclined at 17 degrees with the horizontal. If an average friction force of 4.0x10^3 N impedes the motion, find the speed of the car at the bottom of the driveway.

________m/s (answer)

3. In a circus performance, a monkey is strapped to a sled and both are given an initial speed of 5.0 m/s up a 19 degree inclined track. The combined mass of the monkey and sled is 18 kg, and the coefficient of kinetic friction between sled an incline is 0.20. How far up the incline do the monkey and sled move?

________m (answer)

Explanation / Answer

1.)

By energy conservation-

mgh = 0.5*m(12^2) + 0.5*m(1.3^2)

h=0.5*(145.69)/9.8 = 7.43 m

2.)

By energy conservation-

mg(5.3)*sin(17) - 4.0x10^3*(5.3) = 0.5*m(v^2)

2100(9.8)(5.3)sin(17) - 4.0x10^3*(5.3) =0.5*2100(v^2)

v =3.19 m/s

3.)

By energy conservation-

18g(x)*sin(19) = 0.5*(18)(25) - 18gcos(19)(0.2)*(x)

18gx * (sin(19) + (0.2)cos(19) ) = 0.5*(18)(25)

x = 2.478 m = 2.48 m

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