If the position of a particle varies according to the equations \(x= 3t^2\)${\mathrm{}}^{}$, \(y =2t\), and \(z= 4t+4\), then which of the following is incorrect?

1.	Velocities in \(y\) and \(z\) directions are constant
2.	Acceleration in the \(x\text-\)direction is non-uniform
3.	Acceleration in the \(x\text-\)direction is uniform
4.	Motion is not in a straight line

If three coordinates of a particle change according to the equations \(x = 3 t^{2}, y = 2 t , z= 4\), then the magnitude of the velocity of the particle at time \(t=1\) second will be:
1. \(2\sqrt{11}~\text{unit}\)
2. \(\sqrt{34}~\text{unit}\)
3. \(40~\text{unit}\)
4. \(2\sqrt{10}~\text{unit}\)

Two bodies of equal masses are projected, one from top of the tower in the horizontal direction and other from the foot of tower at an angle of 45° with the horizontal, then the acceleration of their center of mass is

(1) $\frac{\mathrm{g}}{\sqrt{2}}$downward

(2) g downward

(3) $\frac{\mathrm{g}\left(\sqrt{2} - 1\right)}{\sqrt{2}}$ downward

(4) $\frac{\mathrm{g}\left(\sqrt{2} + 1\right)}{\sqrt{2}}$ upward

A projectile is projected at an angle of 60° from horizontal. At an instant, it is moving at an angle of 30° with horizontal with velocity 10 m/s. The radial acceleration of the particle at that instant is:

1.  $\frac{20}{\sqrt{2}}\mathrm{m}/{\mathrm{s}}^2$

2.  $\frac{20}{\sqrt{3}}\mathrm{m}/{\mathrm{s}}^2$

3.  $20\sqrt{3}\mathrm{m}/{\mathrm{s}}^2$

4.  $5\sqrt{3}\mathrm{m}/{\mathrm{s}}^2$

The initial velocity of a projectile is given by $\mathrm{v} = \left(20\hat{\mathrm{i}} + 50\hat{\mathrm{j}} + 70\hat{\mathrm{k}}\right)$ m/s. If acceleration due to gravity is g = 10($-\hat{\mathrm{k}}$) m/${\mathrm{s}}^2$, then the time after which projectile returns to the same horizontal level is:

(1) 4 s

(2) 10 s

(3) 14 s

(4) 12 s

Two persons start moving along two crossroads with the same speed 5 m/s. One in the direction of north and other is in the direction of the east as shown in the figure. Angular velocity of A with respect to B is :

(1) 0.5 m/s

(2) Zero

(3) 1.0 m/s

(4) 2 m/s

In projectile motion, accelerations of the projectile when it is gaining height and losing height respectively are

(1) g upward, g upward

(2) g upward, g downward

(3) g downward, g downward

(4) g downward, g upward

A person, who can swim with speed \(u\) relative to water, wants to cross a river (of width \(d\) and water is flowing with speed \(v\)). The minimum time in which the person can do so is:
1. \(\frac{d}{v}\)
2. \(\frac{d}{u}\)
3. \(\frac{d}{\sqrt{v^{2}   +   u^{2}}}\)
4. \(\frac{d}{\sqrt{v^{2}   -   u^{2}}}\)

The position vector of a particle \(\overrightarrow r\) as a function of time \(t\) (in seconds) is \(\overrightarrow r=3 t \hat{i}+2t^2\hat j~\text{m}\). The initial acceleration of the particle is:
1. \(2~\text{m/s}^2\)
2. \(3~\text{m/s}^2\)
3. \(4~\text{m/s}^2\)
4. zero