Class 9th science mcq question, Short question, Very short Question Answer and MCQ question quiz
MCQs Question Quiz
Part 1.
Video Solution
First law of motion defines-
(A) inertia
(B) force
(C) both inertia and force
(D) neither inertia nor force
Newton's first law of motion is -
(A) qualitative
(B) quantitative
(C) both qualitative and quantitative
(D) neither qualitative nor quantitative
Inertia depends upon -
(A) acceleration of the body
(B) velocity of the body
(C) shape of the body
(D) mass of the body
Which of the following has largest inertia?
(A) A pin
(B) An ink pot
(C) Your physics book
(D) Your body
When a bus starts suddenly the passengers standing on it, lean backwards in the bus. This is an example of -
(A) Newton's first law
(B) Newton's second law
(C) Newton's third law
(D) none of Newton's law
What is the SI unit of momentum?
(A) m/s
(B) Kg m/s
(C) m/s²
(D) None
Name the scientist who gave the laws of motion.
(A) Sir Issac Newton
(B) Elbert Einstein
(C) Alexander Fleming
(D) None of them
When we talk of force acting on a body, it usually means:
(A) Electrical force
(B) Balanced force
(C) Unbalanced force
(D) Nuclear force
A passenger in a moving train tosses a coin which falls behind him. This shows that the motion of train is:
(A) Accelerated
(B) Uniform
(C) Retarded
(D) along circular track
The mass of an object is measured by using
(a) spring balance
(b) litre-jug
(c) weighing machine
(d) physical balance
The product of mass of the object and its velocity is
(a) force
(b) acceleration
(c) weight
(d) momentum
Video Solution
Part 2 .
Video Solution
Rocket works on the principle of conservation of:
(a) mass
(b) energy
(c) momentum
(d) velocity
Among the equal-sized stone and a football, the inertia will be higher of:
(a) football
(b) stone
(c) both
(d) none of them
Friction is:
(a) useful to us
(b) harmful to us
(c) both useful as well as harmful to us
(d) none of them.
Which of the following is the unit of force?
(A) Pascal
(B) Newton
(C) Second
(D) None of them
The physical quantity dependent on direction is
(a) weight
(b) mass
(c) volume
(d) density
The C.G.S. unit of mass is
(a) gram force
(b) gram
(c) kilogram
(d) Newton
The velocity time graph for a constant
velocity is:
(a) Straight line
(b) Curved line
(c) Circular line
(d) All the above
The distance -time graph for uniform motion is a:
(a) Straight line
(b) Curved line
(c) Circular line
(d) All the above
Which one of the following is called first
equation of motion?
(a) v = u + at
(b) s = ut + 1/2 at²
(c) v ² = u² + 2as
(d) All the above
A cyclist does not come to rest immediately after he stops pedalling due to:
(a) Buoyant force
(b) Inertia of motion
(c) Drag force
(d) All the above
Which one of the following formula describes the impulse?
(a) Mass × Acceleration
(b) Force × time
(c) Force/Area
(d) None of them
Upward force exerted by the fluid on the
partially immersed solid in that fluid is called:
(a) Pressure
(b) Buoyant force
(c) Acceleration
(d) Momentum
--------Very Short Question Answer--------
Q 1. Name the scientist who proved for the first time that objects move with constant speed when no force acts on them.
Answer. Galileo.
Q 2. Why do bicycles begin to slow down when we stop pedaling?
Answer. This is because of the frictional forces acting opposite to the direction of motion
Q 3. Which law of motion gives the measure of force?
Answer. Newton's second law of motion.
Q 4. Write the C.G.S unit of force.
Answer. Dyne.
Q 5. Can every force produce motion in every object?
Answer. No.
Q 6. When a force is applied to a body, what are the two essential effect it can produce?
Answer.
(a) It can bring about the change in the state of motion of a body or
(b) It can deform a body, i.e., it can change its shape.
Q 7. Define 1 newton force.
Ans. 1 newton is the magnitude of force which produces an acceleration of I m/s²
in a body of mass 1 kg.
Q 8. What do you mean by an impact force?
Answer. The force produced by the impact of a fast moving object on another is called
impact force.
Q 9. Define force of friction.
Answer. The force acting between any two surfaces in contact and tending to oppose
motion is called force of friction.
Q 10. Define electrostatic force.
Answer. The force exerted by an electrically charged body is called electrostatic force.
Q 11. If the body is found to be accelerated, is the force acting on it balanced or unbalanced?
Answer. Unbalanced.
Q 12. What do balanced forces usually do to a body?
Answer. Balanced forces usually produce a change in the shape of the body.
Q 13. When a body moves on flat surface, will its speed change?
Answer. No.
Q 14. What did Galileo conclude on the basis of his experiments on the motion of
objects?
Answer. A body continues to move with the same velocity if no unbalanced force acts on it.
Q 15. What do you mean by a resultant force?
Answer. When two or more forces act on a body simultaneously, then the single force
which produces the same effect as produced by all the forces acting together is known
as the resultant force.
Q 16. Do action and reaction act on the same body?
Answer. No, action and reaction act on different bodies.
Q 18. Write the SI unit of impulse.
Ans. Ns.
Q 19. What is the total momentum of a bullet and a gun before firing?
Answer. Zero.
Q 20. Name the principle on which a rocket works.
Answer. Newton's third law of motion
Q 21. Body A is heavier than body Q. Which has more inertia?
Answer. A has more inertia.
Q 22. A body is moving with uniform acceleration. Is its momentum constant?
Answer. No.
Q 23. Name the physical quantity that corresponds to the rate of change of momentum.
Answer. Force
Q 24. Which principle is involved in the working of a jet plane?
Answer. Newton's third law of motion.
---------Short Question Answer---------
Q 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?
Answer. A ratio of SI units to CGS units of momentum is (kg m/s)/(g cm/s) i.e., 105
.
The effect of an impulse force on the body is measured only in terms of impulse.
Q 2. On which factors does friction depend?
Answer. The force of friction is directly proportional to the weight of the body sliding over the surface. The force of friction also depends on the nature of the surfaces in contact.
Q 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?
Answer. When the bullet strikes the glass pane, the part of the glass pane which comes in contact with the bullet immediately shares the large velocity of bullet and makes a hole, while the remaining part of the glass remains at rest and is therefore not smashed due
to inertia of rest.
But when a slow moving stone strikes the same glass pane, the various parts of the glass pane gets enough time to share the velocity of the stone, and the glass is smashed.
Q 4. Why can a small mass such as a bullet kill a person when fired from a gun?
Answer. It is so because even if the mass of the bullet is small, it moves out of the gun with a very high velocity, due to which the momentum produced is high (p = mu). This high momentum of the bullet kills a person.
Q 5. Why does a boat tend to leave the shore, when passengers are alighting
from it?
Answer. When the passengers alight from the boat, they push the boat in backward
direction. As a result, the tendency to slip back into water. This difficulty is usually
overcome by the boatman by tying the boat to some rigid support.
Q 6. Describe our walking in terms of Newton's third law of motion.
Answer. When we walk on the ground or road, our foot pushes the ground backward
(action) and the ground pushes our foot forward (reaction). Thus, the forward reaction exerted by the ground on our foot makes us walk forward.
Q 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?
Answer. Steel has the highest inertia. As the mass is a measure of inertia, the ball of same shape and size, having more mass than other balls will have highest inertia. Since steel has greatest density and greatest mass, therefore, it has highest inertia.
Q 8. Why does a cricket player moves his hand backward while catching the ball?
Answer. A fast moving cricket ball has a large momentum. In stopping or catching this ball,
its momentum has reduced to be zero. Now, when a cricket player moves back his
hands on catching the fast ball, then the time taken to reduce the momentum of ball to zero is increased. Due to more time taken to stop the ball, the rate of change of
momentum of ball is decreased and hence a small force is exerted on the hands of
player. So, the hands of player do not get hurt.
Q 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?
Answer. According to conservation of momentum, the rifle recoils with same momentum as
that of bullet. As momentum = mass X velocity; so light rifle will recoil with larger velocity and hence, will hurt the shoulder more.
Q 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.
Answer. The working of the rotation of sprinkler is based on third law of motion. As the water comes out of the nozzle of the sprinkler, an equal and opposite reaction force comes into play. So the sprinkler starts rotating.
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