A boy standing at the top of a tower of 20 m height drops a stone. Assuming \(g=\) 10 ms^-2, the velocity with which it hits the ground is:

1.	20 m/s	2.	40 m/s
3.	5 m/s	4.	10 m/s

A ball is dropped from a high-rise platform at \(t=0\) starting from rest. After \(6\) seconds, another ball is thrown downwards from the same platform with speed \(v\). The two balls meet after \(18\) seconds. What is the value of \(v\)?

A particle moves a distance \(x\) in time \(t\) according to equation \(x=(t+5)^{-1}.\) The acceleration of the particle is proportional to:
1. (velocity)^\(3/2\)
2. (distance)^\(2\)
3. (distance)^\(-2\)
4. (velocity)^\(2/3\)

A particle starts its motion from rest under the action of a constant force. If the distance covered in the first \(10\) s is \(S_1\) and that covered in the first \(20\) s is \(S_2\), then:
1. \(S_2=2S_1\)
2. \(S_2 = 3S_1\)
3. \(S_2 = 4S_1\)
4. \(S_2= S_1\)

The distance travelled by a particle starting from rest and moving with an acceleration \(\frac{4}{3}\) ms^-2, in the third second is:
1. \(6\) m
2. \(4\) m
3. \(\frac{10}{3}\) m
4. \(\frac{19}{3}\) m

A particle shows the distance-time curve as given in this figure. The maximum instantaneous velocity of the particle is around the point:

         

A particle moves in a straight line with a constant acceleration. It changes its velocity from \(10\) ms^-1 to \(20\) ms^-1 while covering a distance of \(135\) m in \(t\) seconds. The value of \(t\) is:

The position of a particle with respect to time \(t\) along the \({x}\)-axis is given by \(x=9t^{2}-t^{3}\) where \(x\) is in metres and \(t\) in seconds. What will be the position of this particle when it achieves maximum speed along the \(+{x} \text-\text{direction}?\)
1. \(32~\text m\)
2. \(54~\text m\)
3. \(81~\text m\)
4. \(24~\text m\)

A car moves from \(X\) to \(Y\) with a uniform speed \(v_u\) and returns to \(X\) with a uniform speed \(v_d.\) The average speed for this round trip is: