A bullet loses $\frac{1}{20}$ of its velocity passing through a plank. The least number of planks required to stop the bullet is (All planks offers same retardation)

1. 10

2. 11

3. 12

4. 23

A body starts from the origin and moves along the X-axis such that the velocity at any instant is given by $(4t^3-2t)$, where t is in sec and velocity in m/s. What is the acceleration of the particle, when it is 2 m from the origin ?

1. 28 m/s²

2. 22 m/s²

3. 12 m/s²

4. 10 m/s²

The relation between time and distance is given by $$\(t=\alpha x^2+\beta x,\) where \(\alpha\) and \(\beta\) are constants. The retardation, as calculated based on this equation, will be (assume \(v\) to be velocity):
1. $\mathrm{}$\(2\alpha v^3\)
2. \(2\beta v^3\)$\mathrm{}{\mathrm{}}^{}$
3. \(2\alpha\beta v^3\)$\mathrm{}{\mathrm{}}^{}$
4. \(2\beta^2 v^3\)$\mathrm{}{\mathrm{}}^{}$

A point moves with uniform acceleration and v₁, v₂ and v₃ denote the average velocities in the three successive intervals of time t₁, t₂ and t₃. Which of the following relations is correct ?

1. $(v_1-v_2):(v_2-v_3)=(t_1-t_2):(t_2+t_3)$

2. $(v_1-v_2):(v_2-v_3)=(t_1+t_2):(t_2+t_3)$

3. $(v_1-v_2):(v_2-v_3)=(t_1-t_2):(t_1-t_3)$

4. $(v_1-v_2):(v_2-v_3)=(t_1-t_2):(t_2-t_3)$ 

The acceleration of a moving body can be found from: 

1. Area under the velocity-time graph

2. Area under the distance-time graph

3. Slope of the velocity-time graph

4. Slope of the distance-time graph

The initial velocity of a particle is u (at t = 0) and the acceleration f is given by at. Which of the following relation is valid 

1. $v=u+a{t}^2$

2. $v=u+a\frac{t^2}{2}$

3. $v=u+at$

4. v = u

The initial velocity of the particle is 10 m/sec and its retardation is 2 m/sec². The distance moved by the particle in 5^th second of its motion is 

1. 1 m

2. 19 m

3. 50 m

4. 75 m

A motor car moving with a uniform speed of 20 m/sec comes to stop on the application of brakes after travelling a distance of 10 m. Its acceleration is 

1. 20 m/sec²

2. –20 m/sec²

3. –40 m/sec²

4. +2 m/sec²

The velocity of a body moving with a uniform acceleration of 2 m/sec² is 10 m/sec. Its velocity after an interval of 4 sec is 

1. 12 m/sec

2. 14 m/sec

3. 16 m/sec

4. 18 m/sec

A particle starting from rest moving with constant acceleration travels a distance x in first 2 seconds and a distance y in next two seconds, then  

1. y = x

2. y = 2x

3. y = 3x

4. y = 4x