Question

After coming down a slope, a 63-kg skier is coasting northward on a level, snowy surface at a constant 15 m/s. Her 5.0-kg cat, initially running southward at 3.5 m/s , leaps into her arms, and she catches it.

a)

Determine the amount of kinetic energy converted to internal energy in the Earth reference frame.(I know this is 790J)

b)***What is the velocity, measured in the Earth reference frame, of an inertial reference frame in which the cat's kinetic energy does not change?

I got 17.14m/s but it's incorrect- what is it?

Answer 1

Apply conservation of linear momentum. (63 kg) (15 m/s)+(5 kg)(-3.5 m/s) (63 kg+5 kg)v (63) (15) (5) (-3.5) (68)v v 13.64 m/s Thus, final kinetic energy is, K, (63 kg+5 kg) (13.64 m/s) -6326 J Initial kinetic energy is K 63 kg) (15 m/s)5 kg) (-3.5 m/s) =7118 J Change in kinetic energy is equal to energy converted into internal energy K,-K,-7118 J-6326 J 790 J The velocity of the skier and cat together wiyh respect to observer in a moving inertial frame is, v 13.64 m/s -3.5 m/s-10.14 m/s