Question:
State Law of conservation of momentum.
Answer:
According to law of conservation of momentum, in the absence of external unbalanced force the total momentum of a system of objects remains unchanged or conserved by collision.
i.e. Total Initial Momentum Before Reaction = Total Initial Momentum After Reaction
This law holds good for any number of objects.
Force and Laws of Motion
Q 1.
What is the unit of force in c.g.s system?
Q 2.
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 3.
Are action-reaction forces simultaneous ?
Q 4.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 5.
On what factor does inertia of a body depend ?
Q 6.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 7.
Can every force produce motion in every object?
Q 8.
Can balanced forces change the shape and size of an object?
Q 9.
In the above question, which body is damaged more ?
Q 10.
Using second law of motion, derive the relation between force and acceleration.
Q 11.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 12.
Explain why a player lowers his hands while catching a cricket ball.
Q 13.
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 14.
What is the SI unit of impulse.
Q 15.
The masses of two objects are 2 kg and 20 kg. Which has greater inertia ?
Q 16.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
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 body of mass 25 kg has momentum of 125 kg m/s. What is the velocity of the body?
Q 19.
What acceleration is produced by a force of 5 N acting on a body of mass 20 kg ?
Q 20.
What is formula of impulse?
Q 21.
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 22.
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 23.
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 24.
State Law of conservation of momentum.
Q 25.
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 26.
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 27.
A bullet of mass 10 g travelling horizontally with a velocity of 150 m/s strikes a stationary wooden 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 28.
Fill in the blanks :
It is dangerous to jump out of a moving bus because due to _________ one falls forward.
Q 29.
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 30.
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 31.
In the following example, try to identify the number of times the velocity of the ball changes:
A football player kicks a football to another player of his team who kicks the football towards the goal. The goalkeeper of the opposite team collects the football and kicks it towards a player of his own team?
Also identify the agent supplying the force in each case.
Q 32.
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 33.
What is collision? What are the types of collision?
Q 34.
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.
Q 35.
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 36.
When a force acting on a body has equal and opposite reaction, then why should the body move at all?
Q 37.
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 38.
Name the three types of inertia.
Q 39.
Name any two applications of the law of conservation of linear momentum.
Q 40.
Explain what is meant by momentum of a body.Is it a scalar or a vector ? What are its units ?
Q 41.
Derive the relation F = ma,where the symbols have their usual meanings.
Q 42.
Discuss briefly Galileo's ideas about motion.
Q 43.
Explain the use of seat belts in cars.
Q 44.
State Newton’s three laws of motion.
Q 45.
State Newton’s first law of motion. Hence define force and inertia.
Q 47.
State Newton's First Law of motion.
Q 48.
Why is it easier to stop a tennis ball in comparison to a cricket ball moving with the same speed ?
Q 49.
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 50.
Name the categories of forces based on interaction.
