Question:
Does Newton's third law apply to a system where bodies do not actually touch each other?
Answer:
Yes, whenever the bodies are in actual contact or even if there is an interaction between the bodies (e.g., attraction or repulsion between two magnets charges, etc.), Newton's third law is applicable.
Force and Laws of Motion
Q 1.
Are action-reaction forces simultaneous ?
Q 2.
On what factor does inertia of a body depend ?
Q 3.
Can every force produce motion in every object?
Q 4.
What is the unit of force in c.g.s system?
Q 5.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 6.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 7.
What is the SI unit of impulse.
Q 8.
Explain why a player lowers his hands while catching a cricket ball.
Q 9.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 10.
The masses of two objects are 2 kg and 20 kg. Which has greater inertia ?
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 body of mass 25 kg has momentum of 125 kg m/s. What is the velocity of the body?
Q 13.
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 14.
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 15.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 16.
Can balanced forces change the shape and size of an object?
Q 17.
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 18.
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 19.
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 20.
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 21.
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 22.
What is the net momentum of gun and bullet system before firing?
Q 23.
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 24.
In the above question, which body is damaged more ?
Q 25.
Using second law of motion, derive the relation between force and acceleration.
Q 26.
Why is the person hurt less when he falls on a spongy surface?
Q 27.
What is formula of impulse?
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.
Why does a gunman get a jerk on a firing a bullet ?
Q 30.
Fill in the blanks :
________ is the tendency of an object to resist a change in motion.
Q 31.
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 32.
Fill in the blanks :
When we shake a branch of a mango tree the mangoes fell down, this happens because of ___________.
Q 33.
When a force acts on a body, what are the two essential effects it can produce?
Q 34.
When you apply a force for a certain amount of time, it creates ________ (fill in the blank).
Q 35.
Which principle is involved in the working of a jet plane?
Q 36.
When a force acting on a body has equal and opposite reaction, then why should the body move at all?
Q 37.
A force of 5 N gives a mass
an acceleration of 10
,and a mass
,an acceleration of 20
.What acceleration would it give if both the masses were tied together ?
Q 38.
A hockey ball of mass 200 g travelling at 10 m/s is struck by a hockey stick so as to return it along its original path with a velocity of 5 m/s.Calculate the change in momentum of the hockey ball by the force applied by the hockey stick.
Q 39.
Name the unbalanced force that stops a ball rolling on the ground.
Q 40.
Show that kg-
and N-s represent the same quantity.Which is that quantity ?
Q 42.
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.
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 45.
Fill in the blanks :
It is dangerous to jump out of a moving bus because due to _________ one falls forward.
Q 46.
Define force of friction.
Q 47.
How is force related to acceleration produced in a body by its application?
Q 48.
Name the physical quantity that corresponds to the rate of change of momentum.
Q 49.
What is the momentum of a man of mass 75 kg when he walks with a velocity of 2 m/s ?
Q 50.
A motorcar is moving with a velocity of 108 km/h and it takes 4 second to stop after the brakes are applied.Calculate the force exerted by the brakes on the motorcar if its mass alongwith the passengers is 1000 kg.
