1) A toddler pushes a box of kittens down a wavy slide with height h = 2m. The m

Question

1) A toddler pushes a box of kittens down a wavy slide with height h = 2m. The magnitude of the work done by friction is 4 J. The box of kittens has a mass of 2 kg. What is the speed of the kittens at the bottom of the slide?

2) A 2 kg ball flies at 4 m/s towards a 2 kg block attached to a spring.

a) If the ball and block collide and stick together, what is the speed of the ball-block system at impact (just before the spring begins to slow them down)?

b) What was the kinetic energy lost in the collision?

c) If the spring constant is k=3200 N/m, how far will the spring compress?

Explanation / Answer

1) KE = mgh - Work done by the friction = 2*9.8*2 - 4 = 35.2 Joules and hence speed = sqrt(2*KE/m) = 5.93 m/sec
2) a) By conservation of momentum, final velocity*mass(2+2) = initial velocity(4)*mass(2) = 2 m/s
   b) KElost = -0.5 * (4*22-2*42) = 8 Joules
   c) KE = (1/2)*k*x2 which gives by KE = 0.5 * (4*22) ; x = 1/200 m = 5mm

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