21.In case of a projectile, what is the angle between the instantaneous velocity and acceleration at the highest point?

22.A particle is projected with a velocity of 30 m/s at an angle of 30 degree to an inclined plane of inclination 30 degree to the horizontal. The particle hits the inclined plane at an angle of 30 degree. The time of impact is:

23.A heavy and a lighter body are dropped from the top of a tower. Which will reach the ground first?

24.An aeroplane is flying horizontally with velocity 150 m/s at a height 100 m from the ground. How long must the distance from the plane to target be, if a bomb is released from the plane to hit the target?

25.A gun is aimed at a horizontal target. It takes 1/2 s for the bullet to reach the target. The bullet hits the target x metre below the aim. Then, x is equal to: