Question:
Name any two applications of the law of conservation of linear momentum.
Answer:
(i) Flight of jet planes and rockets
(ii) Recoiling of a gun on firing.
Force and Laws of Motion
Q 1.
What is the total momentum of a bullet and a gun before firing?
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.
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.
Using second law of motion, derive the relation between force and acceleration.
Q 5.
Are action-reaction forces simultaneous ?
Q 7.
Define momentum of a body.
Q 8.
State Law of conservation of momentum.
Q 9.
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 10.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 11.
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 12.
Give an example that force can make a stationary body move.
Q 13.
What is the net momentum of gun and bullet system before firing?
Q 14.
A constant force acts on an object of mass 5 kg for a duration of 2 s.It increases the object’s velocity from 3 m/s to 7 m/s.Find the magnitude of the applied force. Now if the force were applied for a duration of 5 s,what would be the final velocity of the object ?
Q 15.
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 16.
Is momentum a scalar or vector ?
Q 17.
Discuss briefly Galileo's ideas about motion.
Q 18.
What's the relation between 1N and 1 dyne?
Q 19.
When two objects act on each other, does action-reaction force pair cancel out each other?
Q 20.
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 21.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 22.
Law of conservation of momentum is applicable to an isolated system. What do you mean by an isolated system?
Q 23.
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 24.
The speed-time graph of a car is shown below. The car weighs 1000kg.
(i) Find the distance covered by the in fits two seconds.
(ii) Find how much force is applied by the car brakes in the fifth second so that the car comes to an halt by sixth second.
Q 25.
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 26.
Fill in the blanks :
Which has more inertia of Cricket ball or a rubber ball of the same size? __________
Q 27.
Can balanced forces change the shape and size of an object?
Q 28.
Can every force produce motion in every object?
Q 29.
A person standing in a moving bus falls forward if driver applies brakes suddenly. Name the inertia applying resistance here?
Q 30.
Define force of friction.
Q 31.
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.
Q 32.
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 33.
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 34.
Can balanced forces change the shape and size of a body ?
Q 35.
The masses of two objects are 2 kg and 20 kg. Which has greater inertia ?
Q 36.
What is the SI unit of momentum ?
Q 37.
What is the total momentum of the bullet and the gun on firing ?
Q 38.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 39.
In the above question, which body is damaged more ?
Q 40.
Show that kg-
and N-s represent the same quantity.Which is that quantity ?
Q 41.
Give atleast four applications of Newton’s second law of motion.
Q 42.
What are balanced and unbalanced forces?
Q 43.
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 44.
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 45.
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 46.
Fill in the blanks :
Newton's second law of motion states that the rate of change of ______ of a body is directly proportional to the force and takes place in the same direction as the ______.
Q 47.
Fill in the blanks :
An umbrella protects us from rain it is based on the property of _____________.
Q 48.
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 49.
Fill in the blanks :
________ is a measure of intertia.
Q 50.
Fill in the blanks :
The property of an object to resist changes in its rotational state of motion is called ________.
