Question:
Name the physical quantity whose unit is kg .
Answer:
It is momentum of the body.
Force and Laws of Motion
Q 1.
A man pushes a box of mass 50 kg with a force of 80 N.What will be the acceleration of the box ? What would be the acceleration if the mass were halved ?
Q 2.
A certain force exerted for 1 -2 s raises the speed of an object from 1.8 m/s to 4.2 m/s. Later,the same force is applied for 2 second. How much does the speed change in 2 s ?
Q 3.
Two hockey players of opposite teams,while trying to.hit a hockey ball on the ground collide and immediately become entangled.One has a mass of 60 kg,and was moving with a velocity 5.0 m/s,while the other has a mass of 55 kg and was moving faster with a velocity of 6.0 m/s towards the first player,In which direction and with what velocity will they move after they become entangled ? Assume that the frictional force acting between the feet of the two players and ground is negligible.
Q 4.
Fill in the blanks :
The ______ of an object is a measure of its inertia.
Q 5.
Fill in the blanks :
When we shake a branch of a mango tree the mangoes fell down, this happens because of ___________.
Q 6.
Do balanced forces cause any change of state of an object?
Q 7.
A body is moving with uniform acceleration. Is its momentum constant?
Q 8.
A bullet of mass 50 g is fired from a gun of mass 6 kg with a velocity of 400 m/s.Calculate the recoil velocity of the gun.
Q 9.
A machine gun fires 25 g bullets at the rate of 600 bullets per minute with a speed of 200 m/s.Calculate the force required to keep the gun in position.
Q 10.
A stone of 1 kg is thrown with a velocity if 20
across the frozen surface of a lake and comes to rest after travelling a distance of 50 m.What is the force of friction between the stone and the ice ?
Q 11.
A bullet of mass 10 g travelling horizontally with a velocity of 150
strikes a block and comes to rest in 0.03 s. Calculate the distance of penetration of the bullet into the block.Also, calculate the magnitude of the force exerted by the wooden block on the bullet.
Q 12.
Establish relation between inertia and mass.
Q 13.
What a force can do?
Q 14.
Explain why some of the leaves may get detached from a tree if we vigorously shake its branch.
Q 15.
When a carpet is beaten with a stick, dust comes out of it. Explain.
Q 16.
Two persons manage to push a motorcar of mass 1200 kg at a uniform velocity along a level road. The same motorcar can be pushed by three persons to produce an acceleration of 0.2m s-2. With what force does each person push the motorcar?
(Assume that all persons push the motorcar with the same muscular effort.)
Q 17.
Fill in the blanks :
The momentum of an object is the product of its _____ and _______ and has the same direction as that of the ________.
Q 18.
Fill in the blanks :
When a passenger jumps out of moving bus, he falls down. It is due to _______________.
Q 19.
Fill in the blanks :
A cyclist on a levelled road does not come to rest immediately even he stops pedalling. It is due to ______________.
Q 20.
Fill in the blanks :
When the playing card is flicked with the finger the coin placed over it falls in the tumbler. It is due to ____________.
Q 21.
Why does a bicycle slow down when the cyclist stop pedalling?
Q 22.
Write the SI and CGS unit of force.
Q 23.
What do you mean by a resultant force?
Q 24.
Do action and reaction act on the same body?
Q 26.
What is the SI unit of momentum?
Q 27.
When a force acting on a body has equal and opposite reaction, then why should the body move at all?
Q 28.
What would be the force required to produce an acceleration of 2
in a body of mass 12 kg ? What would be the acceleration if the force were doubled ?
Q 29.
A 150 g ball travelling at 30 m/s strikes the palm of a player’s hand and is stopped in 0 06 sec. Calculate the force exerted by the ball on the hand.
Q 30.
A body of mass 1 kg is kept at rest.A constant force of 6-0 N starts acting on it.Find the time taken by the body to move through a distance of 12 m.
Q 31.
Is momentum a scalar or vector ?
Q 32.
Name the various effects of force.
Q 33.
What is one newton force ?
Q 34.
Show that kg-
and N-s represent the same quantity.Which is that quantity ?
Q 35.
State Newton’s third law of motion and principle of conservation of momentum.
Q 36.
Explain the use of seat belts in cars.
Q 37.
State Newton’s first law of motion. Hence define force and inertia.
Q 38.
State and deduce the principle of conservation of momentum.
Q 39.
A force of 5 N changes the velocity of a body from 10
to 20
in 5 sec.How much force is required to bring about the same change in 2 sec ?
Q 40.
Which of the following has more inertia:
(a) a rubber ball and a stone of the same size?
(b) A bicycle and a train?
(c) A five-rupee coin and a one-rupee coin?
Q 41.
State Newton's First Law of motion.
Q 43.
Which is having higher value of momentum ? A bullet of mass 10 g moving with a velocity of 400 m/s or a cricket ball of mass 400 g thrown with the speed of 90 km/hr.
Q 44.
If the set of forces acting on an object are balanced, then object
(a) must be at rest.
(b) must be moving
(c) must not be accelerating.
(d) none of these.
Q 45.
Why is it advised to tie any luggage kept on the roof of a bus with a rope?
Q 46.
Name the categories of forces based on interaction.
Q 47.
Using second law of motion, derive the relation between force and acceleration.
Q 48.
A stone of 1 kg is thrown with a velocity of 20 m s-1 across the frozen surface of a lake and comes to rest after travelling a distance of 50 m. What is the force of friction between the stone and the ice? (Calculate time taken and acceleration also).
Q 49.
While catching a fast moving ball, fielder gradually pulls his hand backwards. Give reasons.
Q 50.
A man pushes a box of mass 50 kg with a force of 80 N. What will be the acceleration of the box due to this force? What would be the acceleration if the mass were doubled ?
