Question

Force and Laws of Motion Class 9
Extra Questions Very Short Answer Questions
Question 1.
Name the scientist who proved for the first time that objects move with constant speed when no force acts on them.

Question 2.
Why do bicycles begin to slow down when we stop pedalling?

Question 3.
Which law of motion gives the measure of force?

Question 4.
Write the C.G.S unit of force.

Question 5.
Can every force produce motion in every object?

Question 6.
When a force is applied to a body, what are the two essential effects it can produce?

Question 7.
Define 1 newton force.

Question 8.
What do you mean by an impact force?

Question 9.
Define force of friction.

Question 10.
Define electrostatic force.

Question 11.
If the body is found to be accelerated, is the force acting on it balanced or unbalanced?

Question 12.
What do balanced forces usually do to a body?

Question 13.
When a body moves on flat surface, will its speed change?

Question 14.
What did Galileo conclude on the basis of his experiments on the motion of objects?

Question 15.
What do you mean by a resultant force?

Question 16.
Do action and reaction act on the same body?

Question 17.
Plot a graph between force applied on a body and the acceleration produced in the given mass, assuming that the magnitude of force is constantly changing.


Question 18.
Write the SI unit of impulse.

Question 19.
What is the total momentum of a bullet and a gun before firing?

Question 20.
Name the principle on which a rocket works.

Question 21.
Body A is heavier than body B. Which has more inertia?

Question 22.
A body is moving with uniform acceleration. Is its momentum constant?

Question 23.
Name the physical quantity that corresponds to the rate of change of momentum.

Question 24.
Which principle is involved in the working of a jet plane?.

Question 25.
Why mass is sometimes called coefficient of linear inertia?

Question 26.
When a force acting on a body has equal and opposite reaction, then why should the body move at all?

Question 27.
Does Newton’s third law apply to a system where bodies do not actually touch each other?

Question 28.
Suppose a ball of mass m is thrown vertically upwards with an initial speed v, its speed decreases continuously till it becomes zero. Therefore, the ball begins to fall downward and attains the speed v again before striking the ground. It implies that the magnitude of initial and final momenta of the ball are same. Yet, it is not an example of conservation of momentum. Explain why.

Force and Laws of Motion Class 9 Extra Questions Short Answer Questions-I
Question 1.
What is the ratio of SI units to CGS units of momentum? How do you measure the effect of an impulsive force on the body?

Question 2.
On which factors does friction depend?

Question 3.
A bullet fired against a glass window pane makes a hole in it, and the glass pane is not cracked. But on the other hand, when a stone strikes the same glass pane, it gets smashed. Why is it so?

Question 4.
Why can a small mass such as a bullet kill a person when fired from a gun?

Question 5.
Why does a boat tend to leave the shore, when passengers are alighting from it?

Question 6.
Describe our walking in terms of Newton’s third law of motion.

Question 7.
There are three solids made up of aluminium, steel and wood, of the same shape and same volume. Which of them would have highest inertia? [NCERT Exemplar]

Question 8.
Why does a cricket player moves his hand backward while catching the ball?

Question 9.
Two identical bullets are fired one by a light rifle and the other by a heavy rifle with the same force. Which rifle will hurt the shoulder more and why? [NCERT Exemplar]

Question 10.
Water sprinkler used for grass lawns begins to rotate as soon as as the water is supplied. Explain the principle on which it works. [NCERT Exemplar]​

Answer 1

Answer:

question number 6

Explanation:

when we walk ok we push the ground back with a legs and we move forward here Newton's third law of motion is present that is is action is equals to 2 equal and opposite reaction

Answer 2

Answer:

Galileo .

Explanation:

by observation the motion of an objects on the inclined plane Galileo deduced that objects move in a constant speed when nothing force acts on them.