A vector \(\vec {a}\) is turned without a change in its length through a small angle \(d\theta\). The value of \(|\Delta \vec a|\) and \(\Delta a\) are, respectively:

1.	\(0, ad\theta\)	2.	\(a d\theta, 0\)
3.	\(0,0\)	4.	None of these

A steam boat goes across a lake and comes back (a) On a quite day when the water is still and (b) On a rough day when there is uniform air current so as to help the journey onward and to impede the journey back. If the speed of the launch on both days was same, in which case it will complete the journey in lesser time

(1) Case (a)

(2) Case (b)

(3) Same in both

(4) Nothing can be predicted

To a person, going eastward in a car with a velocity of 25 km/hr, a train appears to move towards north with a velocity of $25\sqrt{3}$ km/hr. The actual velocity of the train will be

(1) 25 km/hr

(2) 50 km/hr

(3) 5 km/hr

(4) $5\sqrt{3}$ km/hr

A bus is moving with a velocity 10 m/s on a straight road. A scooterist wishes to overtake the bus in 100 s. If the bus is at a distance of 1 km from the scooterist, with what velocity should the scooterist chase the bus

(1) 50 m/s

(2) 40 m/s

(3) 30 m/s

(4) 20 m/s

The x and y coordinates of the particle at any time are x=5t-2$t^2$ and y=10t respectively, where x and y are in the metres and t is in seconds. The acceleration of the particle at t=2s is :

1. 0

2. 5$m/s^2$

3. -4$m/s^2$

4. -8 $m/s^2$

A particle is moving such that its position coordinates \((x,y)\) are \(​ (2~\text m,  3~\text m)​\) at time \(t=0,\)   \(​ (6~\text m,  7~\text m)​\) at time \(t=2~\text s\)  and \(​ (13~\text m,  14~\text m)​\) at time \(t=5~\text s.\)  The average velocity vector \((v_{avg})\) from \(t=0\) to \(t=5~\text s\) is:

A body is moving with velocity 30 m/s towards east. After 10 s its velocity becomes 40 m/s towards north. The average acceleration of the body is

(1) $7 \mathrm{m}/{\mathrm{s}}^2$                                             

(2) $\sqrt{7} \mathrm{m}/{\mathrm{s}}^2$

(3) $5 \mathrm{m}/{\mathrm{s}}^2$                                             

(4) $1 \mathrm{m}/{\mathrm{s}}^2$

A missile is fired for maximum range with an initial velocity of 20 m/s. If g=10 $\mathrm{m}/{\mathrm{s}}^2$, the range of the missile is

1. 50 m                                                          2. 60 m

3. 20 m                                                          4. 40 m

A projectile is fired at an angle of 45$°$ with the horizontal. The elevation angle of the projectile at its highest point as seen from the point of projection is:

1. 60$°$                                           2. ${\tan }^{-1}\left(\frac{1}{2}\right)$

3. ${\tan }^{-1}\left(\frac{\sqrt{3}}{2}\right)$                               4. $45°$

A particle has initial velocity $\left(3\hat{i}+4\hat{j}\right)$ and has acceleration $\left(0.4\hat{i}+0.3\hat{j}\right)$. Its speed after 10s is 

(1) 7unit                                                         

(2) 7$\sqrt{2}$unit

(3) 8.5 unit                                                     

(4) 10 unit