Скачать или смотреть Exercise Questions | Physics 9th | Chapter 3 | Dynamics | Balochistan Textbook Board, Quetta

1. Encircle the correct option.
What is the measure of Inertia
(a) weight (b) force (c) velocity (d) mass
Momentum is the product of mass and
(a) force (b) velocity (c) acceleration (d) distance
The force which resists the motion of one surface on another surface is known as
(a) momentum (b) weight (c) mass (d) friction
The rolling friction is much _______ than the sliding friction
(a) less (b) greater (c) equal (d) equal or greater
If mass of a body is doubled while the force is kept constant, then the acceleration will be
(a) one half (b) doubled (c) one fourth (d) four times
When a force of 20N acts on a mass of 4kg the acceleration will be
(a) 2〖ms〗^(-2) (b) 5〖ms〗^(-2) (c) 24〖ms〗^(-2) (d) 80〖ms〗^(-2)
Which of the following remains constant everywhere
(a) weight (b) pressure (c) mass (d) velocity
Which is true according to Newton’
(a) m=a/F (b) F=a/m (c) F=m/a (d) m=F/a
When a man jumps from a moving bus. He will fall
(a) towards the moving bus (b) away from the bus
(c) in the direction of motion (d) opposite to the direction of motion
The resisting force between the two surfaces before the motion starts is called the
(a) Kinetic friction (b) Rolling friction (c) Static friction (d) Sliding friction
1. Answer the following questions
What is law of inertia?
Define weight of body.
What is the difference between mass and weight?
Prove Newton’s First Law from Newton’s Second Law of motion.
Explain the tension in the string.
State law of conservation of momentum.
What are the advantages of friction?
What methods are used to reduce friction?
When a gun is fired, it recoils. Why?
Describe two situations in which force of friction is required.
Give two examples of centripetal force.
1. A boy of mass 5kg is moving due east with a velocity of 10〖ms〗^(-1). Find its momentum. What is the direction of momentum?
2. A wooden block of mass 5kg is pushed along a smooth surface of a table with a force of 30N. Find the acceleration of the block.
3. A car of mass 1500kg is moving with velocity of 20〖ms〗^(-1). It is stopped is 5 seconds by applying brakes. Find
(a) What is the average acceleration? (b) How much force is applied? (c) How much distance is covered?
4. An object of mass 10kg is moving with a velocity of 10〖ms〗^(-1). A constant force acts for 4 seconds and reduces its velocity to 2〖ms〗^(-1). Find the momentum before and after application of force.
5. A mass of 5kg is kept moving in a circle of radius 2m with a constant speed of 10〖ms〗^(-1). Find the centripetal force.
6. A block of weighing 10N is lying on the wooden table. The value of μ_s is 0.5 and that of μ_k is 0.4 between the surface of block and table. How much force should be applied horizontally so that
(a) The block may move (b) The block may move with uniform velocity.
7. A smooth block is placed on a smooth wooden table top. A force of 14N is applied to keep 40N block moving at constant speed. (a) What is the co-efficient of sliding friction? (b) If a 20N weight is placed on the forty newton block what force will be required to keep the block with weight moving at a constant velocity?
8. Find the force required to keep a car of mass 2000kg in radius 5m. What it is turning round a corner at 10〖ms〗^(-1)?