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Home › Grade9 › Grade 9 CBSE › Physics › Force and laws of motion › Force and laws of motion Worksheet-6

Force and laws of motion Worksheet-6

Force and laws of motion Worksheet-6

 

  1. Calculate the momentum of a toy car of mass 200 g moving with a speed of 5 m/s.

 

  1. What is the change in momentum of a car weighing 1500 kg when its speed increases from 36 km/h to 72 km/h uniformly?

 

  1. A body of mass 25 kg has a momentum of 125 kg.m/s. Calculate the velocity of the body.

 

  1. Calculate the momentum of the following :

1. an elephant of mass 2000 kg moving at 5 m/s

2. a bullet of mass  200 g moving at 400 m/s

 

  1. Which of the two, balanced forces or unbalanced forces, can change the shape of an object ? Give an example to illustrate your answer.

 

  1. Describe the term 'inertia' with respect to motion.

 

  1. State Newton's first law of motion. Give two examples to illustrate Newton's first law of motion.

 

  1. On what factor does the inertia of a body depend ? Which has more inertia, a cricket ball or a rubber ball of the same size ?

 

  1. Why do the passengers in a bus tend to fall backward when it starts suddenly ?

 

  1. Explain why, a person travelling in a bus falls forward when the bus stops suddenly.

 

  1. Give reason for the following :

When a hanging carpet is beaten with a stick, the dust particles start coming out of it.

 

  1. When a tree is shaken, its fruits and leaves fall down. Why ?

 

  1. Explain why, it is dangerous to jump out of a moving bus.

 

  1. What is the momentum in kg.m/s of a 10 kg car travelling at 5 m/s and 36 km/h ?

 

  1. 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 ?

 

  1. A moving bicycle comes to rest after sometime if we stop pedalling it. But Newton's first law of motion says that a moving body should continue to move for ever, unless some external force acts on it. How do you explain the bicycle case ?

 

  1. Amar throws a ball weighing 500 g vertically upwards with a speed of 10 m/s.

(i) What will be its initial momentum ?

(ii) What would be its momentum at the highest point of its flight ?

 

  1. A car is moving on a level road. If the driver turns off the engine of the car, the car's speed decreases gradually and ultimately it comes to a stop. What could these forces be? Which of these two forces contributes more to slow down and stop the car ?

 

  1. There are two types of forces X and Y. The forces belonging to type X can produce motion in a stationary object but cannot change the shape of the object. On the other hand, forces belonging to type Y cannot produce motion in a stationary object but can change the shape of the object. What is the general name of the forces such as (a) X, and (b) Y ?

 

  1. Which physical quantity corresponds to the rate of change of momentum?

 

Answer:

  1. 1 kg .m/s

 

  1. 15000 kg.m/s

 

  1. 5 m/s . Use the relation : p = mv

 

  1. Using relation p = mv

1. 10000 kg.m/s

2. 8  kg/ms

 

  1. balanced forces

 

  1. Inetia is that property of a body due to which it resists change in its state of rest or motion.

 

  1. A body at rest will remain at rest, and a body in motion will continue in motion in a straight line with a uniform speed, unless it is compelled by an external force to change its state of rest or uniform motion.

 

  1. Mass, Cricket ball because it has more mass than rubber ball. Heavier objects have more inertia than lighter object

 

  1. Because of Intertia

 

  1. Because of Intertia

 

  1. Because of Intertia. The force of stick makes the carpet move but the dust particles remains at rest because of their interia and separate from carpet.

 

  1. Because of Intertia. When tree is shaken it moves to and fro but because of interia the leaves don’t change their position hence they fall.

 

  1. –

 

  1. (a) 50 kg.m/s

(b) 100 kg.m/s

 

  1. The wall will receive equal momentum from both the balls (because both the balls have equal mass and equal velocity)

 

  1. –

 

  1. (i) 5 kg.m/s Using  p = mv

(ii) zero ( velocity at highest point will be zero)

 

  1. Force of friction and Air resistance; force of friction

 

  1. (a) Unbalanced forces

(b) Balanced forces

 

  1. Force