Kinematics 4 Question 8

8. A ball is dropped vertically from a height d above the ground. It hits the ground and bounces up vertically to a height d/2. Neglecting subsequent motion and air resistance, its velocity v varies with height h above the ground as

(2000, 2M)

(a)

(b)

(c)

(d)

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Answer:

Correct Answer: 8. (a)

Solution:

  1. (i) For uniformly accelerated / decelerated motion

v2=u2±2gh

i.e. vh graph will be a parabola (because equation is quadratic).

(ii) Initially velocity is downwards ( ve) and then after collision, it reverses its direction with lesser magnitude, i.e. velocity is upwards (+ve). Graph (a) satisfies both these conditions.

NOTE

At time t=0 corresponds to the point on the graph where h=d.



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