A ball is projected at a certain angle with initial velocity u. It covers horizontal range R. With what initial velocity it should be projected keeping the angle of projection the same so that its horizontal range becomes 2.25R?

1.	2.5u	2.	1.5u
3.	2.25u	4.	0.25u

A particle is moving with velocity $\overrightarrow{\mathrm{v}}=\mathrm{k}(\mathrm{y}\hat{\mathrm{i}}+\mathrm{x}\hat{\mathrm{j}})$ where k is a constant. The general equation for the path will be:

A body is thrown vertically so as to reach its maximum height in t second. The total time from the time of projection to reach a point at half of its maximum height while returning (in second) is:

1. $\sqrt{2}t$

2. $\left(1+\frac{1}{\sqrt{2}}\right)t$

3. $\frac{3t}{2}$

4. $\frac{t}{\sqrt{2}}$

Three particles are moving with constant velocities ${\mathrm{v}}_1,$ ${\mathrm{v}}_2$ and v respectively as given in the figure. After some time, if all the three particles are in the same line, then the relation among ${\mathrm{v}}_1,$ ${\mathrm{v}}_2$ and v is:
                                    
1.  $\mathrm{v}=$ ${\mathrm{v}}_1$ $+$ ${\mathrm{v}}_2$

2.  $\mathrm{v}=$ $\sqrt{{\mathrm{v}}_1{\mathrm{v}}_2}$

3.  $\mathrm{v}=\frac{{\mathrm{v}}_1{\mathrm{v}}_2}{{\mathrm{v}}_1+{\mathrm{v}}_2}$

4.  $\mathrm{v}=$ $\frac{\sqrt{2}{\mathrm{v}}_1{\mathrm{v}}_2}{{\mathrm{v}}_1+{\mathrm{v}}_2}$

A particle starts from the origin at t=0 and moves in the x-y plane with a constant acceleration 'a' in the y direction. Its equation of motion is $y=b{x}^2$. The x component of its velocity (at t=0) will be:

1. variable

2. $\sqrt{\frac{2a}{b}}$

3. $\frac{a}{2b}$

4. $\sqrt{\frac{a}{2b}}$

A boat moves with a speed of 5 km/h relative to water in a river flowing with a speed of 3 km/h. Width of the river is 1 km. The minimum time taken for a round trip will be

1. 5 min

2. 60 min

3. 20 min

4. 30 min

A river is flowing from W to E with a speed of 5 m/min. A man can swim in still water with a velocity of 10 m/min. In which direction should the man swim so as to take the shortest possible path to go to the south. 

1. 30° with downstream

2. 60° with downstream

3. 120° with downstream

4. South

Certain neutron stars are believed to be rotating at about 1 rev/s. If such a star has a radius of 20 km, the acceleration of an object on the equator of the star will be:

In 1.0 s, a particle goes from point A to point B, moving in a semicircle of radius 1.0 m (see figure). The magnitude of the average velocity is:
                   

The angle turned by a body undergoing circular motion depends on the time as given by the equation, $\theta ={\theta }_0+{\theta }_{1}t+{\theta }_2{t}^2$. It can be deduced that the angular acceleration of the body is? 

1. θ₁

2. θ₂

3. 2θ₁

4. 2θ₂