Question

1. A girl weighing 25 kg stands on the floor. She exerts a downward force of 250 N on the floor.
What force does the floor exerts on her?
2. Agun of mass 5kg fires a bullet of mass 40g. The bullet takes 0.003s to move through the barrel
of the gun and acquires a velocity of 100m/s calculate velocity of gun and force exerted by gun.
3. A 2000 kg vehicle moving with a speed of 20m/s is brought to rest in a distance of 40 meters find
96
acceleration and force.
4. A man throws a ball weighing 500 g vertically upward with a speed of 10 m/s what will be its
initial momentum and what would be its momentum at the highest point.
5. What is change in momentum of car weighing 1500 kg when its speed increases from 36km/hr
to 72km/hr uniformly?
6. A force of 10 N gives a mass m1 an acceleration of 12 m/s and mass m2 an acceleration of 30
m/s What acceleration would it give if both the masses are tied together?
V A bullet of mass 20 g moving with a velocity of 500 m/s gets embedded in freely suspended
wooden block of mass 900g what is the velocity acquired by the block?
8. A heavy car A of mass 1000kg travelling at 10m/s has head on collision with a sports car 8 of
mass 500 kg If Both cars stop dead on colliding what was the velocity of car B?
9. An unloaded truck weighing 1000 kg has a maximum acceleration of o.8m/ s 2 what is the
maximum acceleration when it is carrying a load of 2000kg?
10. A girl of mass 50 kg jumps out of a rowing boat of mass 300kg on the bank with horizontal
velocity of 3 m/s with what velocity does the boat begin to move backwards.
11. The car A of mass 2000kg travelling at 20m/s collides with another car B of mass 1500 kg
travelling at 10 m/s in the same direction. After collision the velocity of car A becomes 20 m/s
calculate velocity of car B after the collision.
12. Explain working of rocket.
13. Why runner presses the ground with his feet before he starts his run.
14. Name the physical quantity which makes it easier to accelerate a small car than large car.
15. A plastic ball and a clay ball of equal masses travelling in the same direction with equal speeds
strike against a vertical wall. From which ball does the wall receive a greater amount of
momentum?
16. A moving bicycle comes to rest after some time if we stop pedaling it but Newton's first law of
motion says that a moving body should continue to move forever unless some external force
acts on it. explain for bicycle.
17. A 60 & bullet fired from a 5 kg gun leaves with speed of 500m/s find speed with which the gun
recoils.
18. If action is always equal to reaction explain why a cart pulled by horse can moved.
19. What happens to the passengers travelling in bus takes a sharp turn? Give reasons
20. Describe term inertia with respect to motion.​

Answer 1

1.force of floor on him =-250N

Answer 2

Answer:

Answer:

◆ Answer -

(d) |AB| = 8.5 m

● Explaination -

Let i, j & k be unit vectors along X-axis, Y-axis & Z-axis.

A = i + 2j - 3k

B = 3i + 4j + 5k

Displacement of the man is calculated by -

AB = B - A

AB = (3i + 4j + 5k) - ( i + 2j - 3k)

AB = 2i + 2j + 8k

Magnitude of displacement is calculated by -

|AB| = √(2² + 2² + 8²)

|AB| = √(4 + 4 + 64)

|AB| = √(72)

|AB| = 2√18

|AB| = 8.48 m

From the options, 8.5 m is the most appropriate.