Question:
State Newton’s three laws of motion.
Answer:
Refer to Arts. 2.6,2.11 & 2.15,Pages 84, 87 & 102.
Force and Laws of Motion
Q 1.
While driving on a highway, an insect strikes on the car windshield and splatters. Which experiences greater impact (force): an insect or the windshield?
Q 2.
What is the total momentum of a bullet and a gun before firing?
Q 3.
A car weighs 1500 kg.Its speed time graph is shown in Fig. Calculate the force required at the end of 5 seconds to bring the car to a stop within one second.
Q 4.
On what factor does inertia of a body depend ?
Q 5.
Can balanced forces change the shape and size of an object?
Q 6.
Can balanced forces change the shape and size of a body ?
Q 7.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 8.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 9.
Using second law of motion, derive the relation between force and acceleration.
Q 10.
Are action-reaction forces simultaneous ?
Q 11.
What is the unit of force in c.g.s system?
Q 12.
Can every force produce motion in every object?
Q 13.
In the above question, which body is damaged more ?
Q 14.
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 15.
Honey and Sunny are two friends.Both are financially well off.Honey is fond of driving an SUV while Sunny enjoys driving Tata Nano.Honey explains to Sunny the risks of driving a light vehicle and Sunny explains to Honey the cost factor.
Read the above passage and answer the following questions :
(i) With whom do you agree,with Honey or with Sunny?
(ii) Explain, why?
(iii) Which values of life do you learn from this discussion?
Q 16.
A TV set is lying on a table. The TV set experiences a gravitational force (pull) downwards (FW) by the Earth. It also experiences a force on it due to table in contact i.e. (FTable-TV) in upward direction. Do these forces form an action-reaction pair? Do these forces follow Newton's third Law of motion?
Q 17.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 18.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 19.
A hammer of mass 500 g, moving at 50 m/s, strikes a nail. The nail stops the hammer in a very short time of 0.01 s. What is the force of the nail on the hammer ?
Q 20.
State Law of conservation of momentum.
Q 21.
From a rifle of mass 4 kg, a bullet of mass 50 g is fired with an initial velocity of 35 m/s. Calculate the initial recoil velocity of the rifle.
Q 22.
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 23.
A feather of mass 10 g is dropped from a height.It is found to fall down with a constant velocity.What is the net force acting on it ?
Q 24.
An object experiences a net zero external unbalanced force.Is it possible for the object to be travelling with a non-zero velocity ? If yes,state the conditions that must be placed on the magnitude and direction of the velocity.If no,provide a reason.
Q 25.
What acceleration is produced by a force of 5 N acting on a body of mass 20 kg ?
Q 26.
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 27.
Fill in the blanks :
When a hanging carpet is beaten with stick, the dust particles start coming out of it. It is due to ______________.
Q 28.
For how long should a force of 100 N act on a body of mass 20 kg so that it acquires a velocity of 100 m/s ?
Q 29.
In the above question,which body undergoes greater change in momentum ?
Q 30.
Show that kg-
and N-s represent the same quantity.Which is that quantity ?
Q 31.
Explain why a player lowers his hands while catching a cricket ball.
Q 32.
Give atleast four applications of Newton’s second law of motion.
Q 33.
A body of mass 25 kg has momentum of 125 kg m/s. What is the velocity of the body?
Q 34.
Define 1N (Newton).
Q 35.
A motorcar of mass 1200 kg is moving along a straight line with a uniform velocity of 90 km/h. Its velocity is slowed down to 18 km/h in 4 s by an unbalanced external force. Calculate the acceleration and change in momentum. Also calculate the magnitude of the force required.
Q 36.
Fill in the blanks :
The natural tendency of objects to resist a change in their state of rest or of uniform motion is called ______.
Q 37.
Fill in the blanks :
When we shake a branch of a mango tree the mangoes fell down, this happens because of ___________.
Q 38.
Fill in the blanks :
When a car enters a curved path, the person sitting in it is thrown outwards. This is because of the property of ______________.
Q 39.
Fill in the blanks :
On what factor does the inertia of a body depends? ____________
Q 40.
Fill in the blanks :
When a bus starts suddenly, the bus passengers standing in the bus tend to fall backwards. It is due to _______________.
Q 41.
Fill in the blanks :
________ is the tendency of an object to resist a change in motion.
Q 42.
What are balanced forces?
Q 43.
Define force of friction.
Q 44.
Why do we tend to fall outwards when a car takes a steep turn?
Q 45.
When a body moves on flat friction-less surface, will its speed change?
Q 46.
Is force a scalar or vector quantity?
Q 47.
Name the principle on which a rocket works.
Q 48.
What is the momentum of a man of mass 75 kg when he walks with a velocity of 2 m/s ?
Q 49.
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 50.
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.
