Question

A trolley of mass 200 kg moves with a unifo s1 rm speed of 36 km/h on a frictionless track. speed A child of mass 20 kg runs on the trolley from one end to the other (10 m away) with a of 4 m relative to the trolley in a direction opposite to the its motion, and the trolley. i. What is th ii. e final speed of the trolley ? How much has the trolley moved from t jumps out of he time the child begins to run

Answer 1

From the conservation of momentum:

$$(m+M)V=m(v-u)+Mv$$

$$(20+200)\frac{36}{3.6}=20(v-4)+200v$$

The final speed of the trolley:

$$v=10.4\frac{m}{s}$$

$$t=\frac{d}{v}=\frac{10}{4}=2.5\ s$$

Thus,

$$s=v_1t=(10.4)(2.5)=26\ m$$