Question

2. A 40kg girl is running at a constant speed of 3.6m/s on a straight path toward the edge of an Ice skating ring. At the edge of the ring she jumps on a skateboard (originally at rest). a) What is the mass of the skateboard if the final speed of Sara and the skateboard is observed to be 2.7 m/s? b) Find the ratio of the final to the initial kinetic energy. K.EdK.E.

Answer 1

Given that weight of the girl 40 kgs spend 3.6 m/s (a) form conversation of linear momentum mu = (m + M)V M = Mu/v - m implies M = 13.3 Kg (b) kx final/kE initial = 1/2(m + M) V^2/1/2mu^2 kx final/kE initial = (m + M)/m times (v/u)^2 kx final/kE initial = (40 + 1.33/40) (2.7/3.6)^2 = 5(41.33/40)(2.7/3.6)^2 kx final/kE initial = 0.75