The initial velocity of a body moving along a straight line is 7 m/s. It has a uniform acceleration of 4 m/s². The distance covered by the body in the 5^th second of its motion is  

1. 25 m

2. 35 m

3. 50 m

4. 85 m

The velocity of a body depends on time according to the equation $v=20+0.1t^2$. The body is undergoing 

1. Uniform acceleration

2. Uniform retardation

3. Non-uniform acceleration

4. Zero acceleration

Which of the following four statements is false?

1. A body can have zero velocity and still be accelerated.

2. A body can have a constant velocity and still have a varying speed.

3. A body can have a constant speed and still have a varying velocity.

4. The direction of the velocity of a body can change when its acceleration is constant.

The position of a particle moving in the XY plane at any time t is given by $x=(3t^2-6t)$ metres. Select the correct statement about the moving particle from the following.

1. The acceleration of the particle is zero at t = 0 second
2. The velocity of the particle is zero at t = 0 second
3. The velocity of the particle is zero at t = 1 second
4. The velocity and acceleration of the particle are never zero

If body having initial velocity zero is moving with uniform acceleration 8 m/sec² , then the distance travelled by it in fifth second will be  

1. 36 metres

2. 40 metres

3. 100 metres

4. Zero

An alpha particle enters a hollow tube of 4 m length with an initial speed of 1 km/s. It is accelerated in the tube and comes out of it with a speed of 9 km/s. The time for which it remains inside the tube is

1. $8\times {10}^{-3} s$

2. $80\times {10}^{-3}s$

3. $800\times {10}^{-3}s$

4. $8\times {10}^{-4}s$

Two cars $A$ and $B$ are travelling in the same direction with velocities $v_1$ and $v_2 (v_1>v_2)$. When the car $A$ is at a distance $d$ behind car $B$, the driver of the car $A$ applied the brake producing uniform retardation $a$. There will be no collision when:
1. $d< \dfrac{(v_1-v_2)^2}{2a}$

2. $d< \dfrac{v^2_1-v^2_2}{2a}$

3. $d> \dfrac{(v_1-v_2)^2}{2a}$

4. $d> \dfrac{v^2_1-v^2_2}{2a}$

A body of mass 10 kg is moving with a constant velocity of 10 m/s. When a constant force acts for 4 seconds on it, it moves with a velocity 2 m/sec in the opposite direction. The acceleration produced in it is 

1. 3 m/sec²

2. –3 m/sec²

3. 0.3 m/sec²

4. –0.3 m/sec²