CBSE
A passenger train is moving at 5 ms-1 .An express train is travelling at 30 ms-1, on the same track and rear side of the passenger train at some distance. The driver in express train applied brakes to avoid collision. If the retardation due to brakes is 4 ms-2 , the time in which the accident is avoided after the application of brakes is
4.25 s
5.25 s
6.25 s
7.25 s
The acceleration experienced by a moving boat after its engine is cut off, is given by a = − kv3, where k is a constant. If v0 is the magnitude of velocity at cut off, then the magnitude of the velocity at time t after the cut off is
The magnitude of vectors A, B and C are 3, 4 and 5 units respectively. If A + B =C, then the angle between A and B is
cos-1 0.6
tan-1
The magnitude of a vector, on the addition of two vectors is
A 10 kg object collides with stationary 5 kg object and after collision they stick together and move forward with velocity 4 ms-1. What is the velocity with which the 10 kg object hit the second one ?
4 ms-1
6 ms-1
10 ms-1
12 ms-1
A body starting from rest moves with constant acceleration. The ratio of distance covered by the body during the 5th second to that covered in 5 s is
An object is projected at an angle of 45° with the horizontal. The horizontal range and maximum height reached will be in the ratio
1 : 2
2 : 1
1 : 4
4 : 1
A particle is projected upwards from the surface of the earth (of radius R) with a KE equal to half the minimum value needed for it to escape. To what height (h) does it rise above the surface of the earth
R
2R
(R)1/2
An aeroplane is flying horizontally with a velocity of 600 km/h and at a height of 1960 m. When it is vertically above a point A on the ground a bomb is released from it. The bomb strikes the ground at point B. The distance AB is
1200 m
0.33 km
333.3 km
3.33 km
A particle of mass m is projected with velocity v making an angle of 45° with the horizontal. When the particle lands on the level ground, the magnitude of the change in momentum is
along -ve y-direction
along +ve y-direction
along -ve y-direction
along +ve y-direction