Question

MCQ
3)A student drops a ball from a slope. He notices the ball rolling down as shown in
the image.
Which of these statements is true about the motion?
(a)The student is in motion as he is standing.
(b)The student is in motion as he drops the ball.
(c)The ball is in motion as it rolls down the slope.
(d)The ball is in motion as its shape changes over time.

Answer 1

Answer:

iii only

Force acting on the ball is same in both the cases, therefore acceleration will also be same a1​=a2​. Thus, (ii) is wrong.

S=Ut+2at2​

Initially ball is at rest, U=0

S=2at2​

So, we see that: S∝t2

Now, as the distance travelled by the two balls are S1​sinθ=h and S2​sinθ=2h

S2​S1​​=21​

S2​=2S1​

So, we get: t2​=2

​t1​

Thus (i) is wrong.

The acceleration in both cases i.e at position P as well as Q is g, acting in vertically downward direction.  Thus (ii) is  also wrong.

Now by Conservation of Energy formula, the potential energy possessed by the ball is converted to its Kinetic energy at the bottom of the inclined plane.

PE at point Q = mg(2h) ; PE at point P = mg(h)

Thus, KE at O (when ball falls from Q) = KE at O (when ball falls from P)

So, (iii) is correct.

Explanation:

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