Question:
Explain briefly any three applications of Newton’s third law of motion.
Answer:
Refer to Art. 2.16, Page 102.
Force and Laws of Motion
Q 1.
Are action-reaction forces simultaneous ?
Q 2.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 3.
Can every force produce motion in every object?
Q 4.
On what factor does inertia of a body depend ?
Q 5.
What is the unit of force in c.g.s system?
Q 6.
Explain why a player lowers his hands while catching a cricket ball.
Q 7.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 8.
What is the SI unit of impulse.
Q 9.
The masses of two objects are 2 kg and 20 kg. Which has greater inertia ?
Q 10.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 11.
An object of mass 1 kg travelling in a straight line with a velocity of 10 m/s collides with, and sticks to, a stationary wooden block of mass 5 kg. Then they both move off together in the
same straight line. Calculate the total momentum just before the impact and just after the impact. Also, calculate the velocity of the combined object.
Q 12.
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 ?
Q 13.
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 14.
A body of mass 25 kg has momentum of 125 kg m/s. What is the velocity of the body?
Q 15.
Can balanced forces change the shape and size of an object?
Q 16.
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 17.
What is the net momentum of gun and bullet system before firing?
Q 18.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 19.
Derive the relation F = ma,where the symbols have their usual meanings.
Q 20.
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 21.
State Newton’s second law of motion and establish that F = ma where symbols have their usual meanings.
Q 22.
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 23.
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 24.
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 25.
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 26.
When a force acts on a body, what are the two essential effects it can produce?
Q 27.
What is the total momentum of a bullet and a gun before firing?
Q 28.
Which principle is involved in the working of a jet plane?
Q 29.
Two objects of masses 100 g and 200 g are moving along the same line in the same direction with velocities of 2 m/s and 1 m/s,respectively.They collide and after the collision, the first object moves at a velocity of 1.67 m/s in the same direction.Determine the velocity of the second object
Q 30.
Is momentum a scalar or vector ?
Q 31.
A person in a bus tends to fall backwards, when it starts suddenly ?
Q 32.
A ball is thrown vertically upwards. What is its momentum at the highest point ?
Q 33.
Why does a gunman get a jerk on a firing a bullet ?
Q 34.
State Newton’s first law of motion. Hence define force and inertia.
Q 35.
Give atleast four applications of Newton’s second law of motion.
Q 37.
What a force can do?
Q 38.
Is force required to keep a moving object in motion (yes/no)?
Q 39.
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 40.
Why is it advised to tie any luggage kept on the roof of a bus with a rope?
Q 41.
State Newtons second law of motion.
Q 42.
Define 1N (Newton).
Q 43.
An object of mass 5 kg is moving with a velocity 4 m/s. A constant force of 20 N acts on the object. What will be the velocity after 3 s.
Q 44.
If action is always equal to the reaction, explain how a horse can pull a cart.
Q 45.
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 46.
Using a horizontal force of 200 N, we intend to move a wooden cabinet across a floor at a constant velocity. What is the friction force that will be exerted on the cabinet?
Q 47.
State Law of conservation of momentum.
Q 48.
Law of conservation of momentum is applicable to an isolated system. What do you mean by an isolated system?
Q 49.
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 50.
A hockey ball of mass 200 g travelling at 10 m s-1 is struck by a hockey stick so as to return it along its original path with a velocity at 5 m s-1. Calculate the change of momentum occurred in the motion of the hockey ball by the force applied by the hockey stick.
