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.
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.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 4.
Are action-reaction forces simultaneous ?
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.
In the above question, which body is damaged more ?
Q 9.
Can balanced forces change the shape and size of an object?
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.
The masses of two objects are 2 kg and 20 kg. Which has greater inertia ?
Q 13.
Explain why a player lowers his hands while catching a cricket ball.
Q 14.
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 15.
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 16.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 17.
What is the SI unit of impulse.
Q 18.
What acceleration is produced by a force of 5 N acting on a body of mass 20 kg ?
Q 19.
A body of mass 25 kg has momentum of 125 kg m/s. What is the velocity of the body?
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.
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.
What is formula of impulse?
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.
What is collision? What are the types of collision?
Q 26.
Fill in the blanks :
It is dangerous to jump out of a moving bus because due to _________ one falls forward.
Q 27.
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 28.
Derive the relation F = ma,where the symbols have their usual meanings.
Q 29.
While catching a fast moving ball, fielder gradually pulls his hand backwards. Give reasons.
Q 30.
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 31.
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 32.
When a force acting on a body has equal and opposite reaction, then why should the body move at all?
Q 33.
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 34.
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 35.
Is force a scalar or a vector ?
Q 37.
Name any two applications of the law of conservation of linear momentum.
Q 38.
State Newton's First Law of motion.
Q 39.
If action is always equal to the reaction, explain how a horse can pull a cart.
Q 40.
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 41.
Fill in the blanks :
When we shake a branch of a mango tree the mangoes fell down, this happens because of ___________.
Q 42.
Fill in the blanks :
Which has more inertia of Cricket ball or a rubber ball of the same size? __________
Q 43.
Fill in the blanks :
When a hanging carpet is beaten with stick, the dust particles start coming out of it. It is due to ______________.
Q 44.
What is the total momentum of a bullet and a gun before firing?
Q 45.
What would be the force required to produce an acceleration of 2
in a body of mass 12 kg ? What would be the acceleration if the force were doubled ?
Q 46.
A 150 g ball travelling at 30 m/s strikes the palm of a player’s hand and is stopped in 0 06 sec. Calculate the force exerted by the ball on the hand.
Q 47.
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 48.
What is the momentum of an object of mass m,moving with a velocity v ?(a)
(b)
(c)
(d) mv
Q 49.
What is the SI unit of momentum ?
Q 50.
Show that kg-
and N-s represent the same quantity.Which is that quantity ?
