A force of 10 N acts on a body of mass 20 kg for 10 seconds.Change in its momentum is

5 kg m/s
100 kg m/s
200 kg m/s
1000 kg m/s

Solution

Change in momentum = F × t= 10 × 10 = 100 Ns or 100 kg. m/s

A particle of mass m is moving with velocity v1, it is given an impulse such that the velocity becomes v2. Then magnitude of impulse is equal to

\(m(\dot{V}_{2}-\dot{V}_{1})\)
\(m(\dot{V}_{1}-\dot{V}_{2})\)
\(m\times (\dot{V}_{2}-\dot{V}_{1})\)
\(0.5m\times (\dot{V}_{2}-\dot{V}_{1})\)

Solution

Impulse =change in momentum =\(m\dot{V}_{2}-m\dot{V}_{1}\)

A body of mass 4 kg moving on a horizontal surface with an initial velocity of 6 ms^-1 comes to rest after 3 seconds. If one wants to keep the body moving on the same surface with the velocity of 6 ms^-1, the force required is

Zero
4 N
8 N
16 N

Solution

Acceleration,a=\(\frac{v-u}{t}=\frac{0-6}{3}=-2\: ms^{-2}\)

Force = m×a = 4×2 = 8 N

A monkey is climbing up a rope, then the tension in the rope

must be equal to the force applied by the monkey on the rope
must be less than the force applied by the monkey on the rope.
must be greater than the force applied by the monkey on the rope.
may be equal to, less than or greater the force applied by the monkey on the rope.

The direction of impulse is

same as that of the net force
opposite to that of the net force
same as that of the final velocity
same as that of the initial velocity

A body is moving with uniform velocity, then

no force must be acting on the body.
exactly two forces must be acting on the body
body is not acted upon by a single force.
the number of forces acting on the body must be even

The force of action and reaction

must be of same nature
must be of different nature
may be of different nature
may not have equal magnitude

When a horse pulls a cart, the horse moves down to

horse on the cart.
cart on the horse.
horse on the earth.
earth on the horse

Centripetal force :

can change speed of the body.
is always perpendicular to direction of motion
is constant for uniform circular motion.
all of these

A rectangular block is placed on a rough horizontal surface in two different ways as shown, then

friction will be more in case (a)
friction will be more in case (b)
friction will be equal in both the cases
friction depends on the relations among its dimensions.

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