The rocket engines lift a rocket from the earth because hot gases with high velocity
push it against the earth
push it against the air
react against rocket and push it up
heat up the air which lifts the rocket
A block is lying static on the floor.The maximum value of static frictional force on the block is 10 N.If a horizontal force of 8 N is applied to the block,what will be the frictional force on the block ?
2 N
18 N
8 N
10 N
A cricket player catches a ball of mass 100g and moving with a velocity of 25ms-1. If the ball is caught in 0.1s, the force of the blow exerted on the hand of the player is
4N
25N
40N
250N
For a car not to turn safely on a curved road
speed in slow
distance between tyres in large
centre of gravity for car is low
low friction force
An army vehicle of mass 1000 kg is moving with a velocity of 10 m/s and is acted upon by a forward force of 1000 N due to engine and a retarding force of 500 N due to friction.What will be its velocity after 10 sec ?
5 m/s
10 m/s
15 m/s
20 m/s
A 500 kg car takes a round turn of radius 50 m with a velocity of 36 km/hr. The centripetal force is
1000 N
750 N
250 N
1200 N m/s
Smoothening the surface contact beyond a certain limit raises friction because
irregularities are increased
surface projections are sharpened
area of actual contact increases
none of the above reasons
A body takes time t to reach the bottom of an inclined plane of angle θ with the horizontal. If the plane is made rough, time taken now is 2t. The coefficient of friction of the rough surface is
If μs is coefficient of static friction and μk is coefficient of kinetic friction, then
there is no relation between μs and μk
generally μs>μk
generally, μs=μk
generally μsk
A man of mass 75 kg is standing in an elevator which is moving with an acceleration of 5 m/s2 in upward direction. The apparent weight of the man will be (g=10 m/s2)
1125 N
1375 N
1250 N
1425 N
