Question:
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.
Answer:
Given, mass of object (m1) = 1 kg
initial velocity of object before collision (u1) = 10 m/s
mass of wooden block (m2) = 5kg
velocity of wooden block before collision (u2) = 0 m/s
final velocity of object+wooden black (v) after collision = ? m/s
Since momentum is conserved,
total initial momentum = total final momentum
i.e. (m1u1) + (m2u2) = (m1+ m2)v
⇒ 1 × 10 + 0 = (1 + 5)v
⇒ v = 10/6 m/s = 5/3 m/s
Initial momentum = (m1u1) + (m2u2) = 1 × 10 + 0 = 10 kg m/s
Final momentum = (m1+ m2)v = (1 + 5) × (5/3) = 6 × (5/3) = 10 kg m/s
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.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 3.
On what factor does inertia of a body depend ?
Q 4.
Using second law of motion, derive the relation between force and acceleration.
Q 5.
What is the unit of force in c.g.s system?
Q 6.
In the above question, which body is damaged more ?
Q 7.
Can every force produce motion in every object?
Q 8.
Are action-reaction forces simultaneous ?
Q 9.
Explain why a player lowers his hands while catching a cricket ball.
Q 10.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 11.
Can balanced forces change the shape and size of a body ?
Q 12.
Can balanced forces change the shape and size of an object?
Q 13.
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 14.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 15.
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 16.
What acceleration is produced by a force of 5 N acting on a body of mass 20 kg ?
Q 17.
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 18.
Explain what is meant by momentum of a body.Is it a scalar or a vector ? What are its units ?
Q 19.
What is the total momentum of a bullet and a gun before firing?
Q 20.
State Newton’s first law of motion. Hence define force and inertia.
Q 21.
What a force can do?
Q 22.
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 23.
Fill in the blanks :
On what factor does the inertia of a body depends? ____________
Q 24.
What is one newton force ?
Q 25.
Which of the following has more inertia:
(a) a rubber ball and a stone of the same size?
(b) A bicycle and a train?
(c) A five-rupee coin and a one-rupee coin?
Q 26.
State why Newton's first law of motion is called law of inertia.
Q 27.
A body of mass 25 kg has momentum of 125 kg m/s. What is the velocity of the body?
Q 28.
State Newtons second law of motion.
Q 29.
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 30.
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 31.
Fill in the blanks :
An imaginary co-ordinate system which is either at rest or in uniform and where Newton's laws are valid is called an _______ frame of reference.
Q 32.
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 33.
Fill in the blanks :
It is dangerous to jump out of a moving bus because due to _________ one falls forward.
Q 34.
Name the physical quantity that corresponds to the rate of change of momentum.
Q 35.
Why mass is sometimes called coefficient of linear inertia?
Q 36.
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 37.
Derive the unit of force using the second law of motion. A force of 5 N produces an acceleration of
on a mass
and an acceleration of 24
on a mass
.What acceleration would the same force provide if both the masses are tied together ?
Q 38.
Is force a scalar or a vector ?
Q 39.
The masses of two objects are 2 kg and 20 kg. Which has greater inertia ?
Q 40.
Explain the use of seat belts in cars.
Q 41.
Explain briefly any three applications of Newton’s third law of motion.
Q 42.
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 43.
State Newton's First Law of motion.
Q 44.
Why is it easier to stop a tennis ball in comparison to a cricket ball moving with the same speed ?
Q 45.
When a carpet is beaten with a stick, dust comes out of it. Explain.
Q 46.
While catching a fast moving ball, fielder gradually pulls his hand backwards. Give reasons.
Q 47.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 48.
Fill in the blanks :
An umbrella protects us from rain it is based on the property of _____________.
Q 49.
Which Newton's law is also known as the Law of Inertia?
Q 50.
What did Galileo conclude on the basis of his experiments on the motion of objects?
