A man is at a distance of 6 m from a bus. The bus begins to move with a constant acceleration of 3ms.In order to catch the bus, the minimum speed with which the man should run towards the bus is
2 m s-1
4 m s-1
6 m s-1
8 m s-1
C.
6 m s-1
If the man did not run, the bus would be at a distance s1 at time t given by
s1 = 6 + t2
= 6 + × 3 × t2
s1 = 6 + t2
If v is the speed of man, he would cover a distance s2 = vt in time t.
To catch the bus,
s1 = s2
6 + t2 = v t
⇒ t2 t + 4 = 0
which gives
t =
Now t will be real if is positive or zero.
Minimum v corresponds to = 0 which gives v = 6 m s-1
A gun of mass 10 kg fires 4 bullets per second. The mass of each bullet is 20 g and the velocity of the bullet when it leaves the gun is 300 m s-1. The force required to hold the gun when firing is
6 N
8 N
24 N
240 N
A stone of mass 0.3 kg attached to a 1.5 m long string is whirled around in a horizontal circle at a speed of 6 m s-1 The tension in the string is
10 N
20 N
7.2 N
30 N
A ball is dropped from the top of a building 100 m high. At the same instant another ball is thrown upwards with a velocity of 40 m/s from the bottom of the building. The two balls will meet after
3 s
2 s
2.5 s
5 s
If the linear momentum is increased by 50%, then kinetic energy will increase by
0 %
100 %
125 %
25 %
The additional kinetic energy to be provided to a satellite of mass m revolving around a planet of mass M to transfer it from a circular orbit of radius R, to another of radius R2 (R2 > R1 ) is
GmM
GmM
2 GmM
GmM
A sphere of mass 10 kg and radius 0.5 m rotates about a tangent. The moment of inertia of the sphere is
5 kg m2
2.7 kg m2
3.5 kg m2
4.5 kg m2
A body moves from rest with a constant acceleration. Which one of the following graphs represents the variation of its kinetic energy K with the distance travelled (x)?