# Numerical Problems from Kinematics and Force

1.if a man in a boat rows perpendicular to the bank he is drifted 120 m during crossing river in 10 minutes . if he heads at angle of alpha from upstream he crosses river by shortest path in 12.5 min.
find width of river,velocity of river with respect to water,velocity of boat with respect to river

2.a projectile is thrown horizontally from top of building of height 10 m with a certain speed u.at same time another projectile thrown from ground 10 m away from building with equal speed u in same vertical plane at angle theta with horizontal.if they collide after 1 second then find u and angle of projections of 1st and 2nd particle

3.a 10 kg block is resting on a rough surface .when force is applied to it for 4s. the variation of force with time is given as (f=100N for 4s.). also (coefficient of friction=0.5) find velocity at t=1s and t=4s.

4. a particle moves in straight line whose acceleration depends on velocity as a=-alpha root v, alpha =+ve constant . at initial moment velocity of particle is Vo.if average speed before it stops is Vo/x find value of x.