Page 110 - Understanding NCERT Science 09

said that both the motorcar and the insect experienced the
same force and a change in their momentum. Comment on
these suggestions.
17. How much momentum will a dumb-bell of mass 10 kg
transfer to the floor if it falls from a height of 80 cm? Take
–2
its downward acceleration to be 10 m s .
Additional

Exercises

A1. The following is the distance-time table of an object in
motion:
Time in seconds Distance in metres
0 0
1 1
2 8
3 27
4 64
5 125
6 216
7 343
(a) What conclusion can you draw about the acceleration?
Is it constant, increasing, decreasing, or zero?
(b) What do you infer about the forces acting on the object?
A2. Two persons manage to push a motorcar of mass 1200 kg at
a uniform velocity along a level road. The same motorcar
can be pushed by three persons to produce an acceleration
of 0.2 m s . With what force does each person push the
-2
motorcar? (Assume that all persons push the motorcar with
the same muscular effort.)
-1
A3. A hammer of mass 500 g, moving at 50 m s , strikes a nail.
The nail stops the hammer in a very short time of 0.01 s.
What is the force of the nail on the hammer?
A4. A motorcar of mass 1200 kg is moving along a straight line
with a uniform velocity of 90 km/h. Its velocity is slowed
down to 18 km/h in 4 s by an unbalanced external force.
Calculate the acceleration and change in momentum. Also
calculate the magnitude of the force required.

FORCE AND LAWS OF MOTION 99

Rationalised 2023-24