Figure 13 shows a frictionless trolley of mass 2kg moving with uniform velocity
towards a wall. At the front of the trolley is a spring whose spring constant is 25 Nm-1. The
trolley comes to rest momentarily after compressing the spring by 3cm and the rebounds from the wall.

(i) Determine:
(I) The force exerted on the wall by the spring.
(II) The maximum acceleration of the as it rebounds from the wall.
(ii) State the reason why the trolley acquires a constant velocity after it rebounds.

Answer:

i)
I)F=ke

25x0.03=0.75N

II) F=ma

therefore, 0.75=2a

a=0.375#ms^-2#

ii)- Force in spring decreases as spring recovers original length. No force on
trolley after contact with wall is lost.

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