A body is projected with a speed u m/s at an angle β with the horizontal. The kinetic energy at the highest point is th of the initial kinetic energy. The value of β is
30°
45°
60°
120°
A ball is projected horizontally with a velocity of 5 m/s from the top of a building 19.6 m high. How long will the ball take to hit the ground ?
2 s
3 s
A stone falls freely from rest and the total distance covered by it in the last second of its motion equals the distance covered by it in the first three seconds of its motion. The stone remains in the air for
6 s
5 s
7 s
4 s
Two blocks of 2 kg and 1 kg are in contact on a frictionless table. If a force of 3 N is applied on 2 kg block, then the force of contact between the two blocks will be
zero
1 N
2 N
3 N
B.
1 N
Acceleration of both the blocks taken together =
Hence, the contact force between the two blocks is equal to
1 kg × 1 m/s2 = 1 N
A boy of mass 40 kg is climbing a vertical pole at a constant speed. If the coefficient of friction between his palms and the pole is 0.8 and g = 10 m/s2, the horizontal force that he is applying on the pole is
300 N
400 N
500 N
600 N
The height vertically above the earth's surface at which the acceleration due to gravity becomes 1% of its value at the surface is (R is the radius of the earth)
8 R
9 R
10 R
20 R
The change in the gravitational potential energy when a body of mass m is raised to a height nR above the surface of the Earth is (Here R is the radius of the earth)
nmgR