The position-time \((x\text-t)\) graph for positive acceleration is:

1.		2.
3.		4.

The figure given below shows the displacement and time, \((x\text -t)\) graph of a particle moving along a straight line:
           
The correct statement, about the motion of the particle, is:

A stone is thrown vertically downwards with an initial velocity of \(40\) m/s from the top of a building. If it reaches the ground with a velocity of \(60\) m/s, then the height of the building is: (Take \(g=10\) m/s²)
1. \(120\) m
2. \(140\) m
3. \(80\) m
4. \(100\) m

A scooter accelerates from rest for time \(t_1\) at constant rate \(a_1\) and then retards at constant rate \(a_2\) for time \(t_2\) and comes to rest. The correct value of  \(\frac{t_1}{t_2}\) will be:
1. \(\frac{a_1+a_2}{a_2}\)
2. \(\frac{a_2}{a_1}\)
3. \(\frac{a_1}{a_2}\)
4. \(\frac{a_1+a_2}{a_1}\)

Train \(A\) and train \(B\) are running on parallel tracks in the opposite directions with speeds of \(36~\text{km/hour}\) and \(72~\text{km/hour}\), respectively. A person is walking in train \(A\) in the direction opposite to its motion with a speed of \(1.8~\text{km/hour}\). Speed (in ms^–1) of this person as observed from train \(B\) will be close to : (take the distance between the tracks as negligible)
1. \(30.5\) ms^–1
2. \(29.5\) ms^–1
3. \(31.5\) ms^–1
4. \(28.5\) ms^–1

A small block slides down on a smooth inclined plane starting from rest at time \(t=0.\) Let \(S_n\) be the distance traveled by the block in the interval \(t=n-1\) to \(t=n.\) Then the ratio \(\frac{S_n}{S_{n +1}}\) is:
1. \(\frac{2n+1}{2n-1}\)
2. \(\frac{2n}{2n-1}\)
3. \(\frac{2n-1}{2n}\)
4. \(\frac{2n-1}{2n+1}\)