Question:
A man pushes a box of mass 50 kg with a force of 80 N.What will be the acceleration of the box ? What would be the acceleration if the mass were halved ?
Answer:
1.6 ; 3.2
Force and Laws of Motion
Q 1.
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 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.
Can balanced forces change the shape and size of an object?
Q 4.
What is the total momentum of a bullet and a gun before firing?
Q 5.
Are action-reaction forces simultaneous ?
Q 6.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 7.
Can balanced forces change the shape and size of a body ?
Q 8.
On what factor does inertia of a body depend ?
Q 9.
Using second law of motion, derive the relation between force and acceleration.
Q 10.
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 11.
Can every force produce motion in every object?
Q 12.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 13.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 14.
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 15.
What is the unit of force in c.g.s system?
Q 16.
State Law of conservation of momentum.
Q 17.
In the above question, which body is damaged more ?
Q 18.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 19.
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 20.
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 21.
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 22.
A man pushes a box of mass 50 kg with a force of 80 N.What will be the acceleration of the box ? What would be the acceleration if the mass were halved ?
Q 23.
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 24.
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 26.
Why does a person in a bus tend to fall forward when it stops suddenly ?
Q 27.
Discuss briefly Galileo's ideas about motion.
Q 28.
A body of mass 25 kg has momentum of 125 kg m/s. What is the velocity of the body?
Q 29.
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 30.
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 31.
Give an example that force can make a stationary body move.
Q 32.
When a force acts on a body, what are the two essential effects it can produce?
Q 33.
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 34.
What are unbalanced forces ?
Q 35.
Why does a gun recoil on firing ? Obtain an expression for recoil velocity of gun.
Q 36.
Give atleast four applications of Newton’s second law of motion.
Q 37.
Why is it advised to tie any luggage kept on the roof of a bus with a rope?
Q 38.
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 39.
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 40.
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 41.
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 42.
Why does a bicycle slow down when the cyclist stop pedalling?
Q 43.
Is force a scalar or vector quantity?
Q 44.
Why is the person hurt less when he falls on a spongy surface?
Q 45.
What is the momentum of a man of mass 75 kg when he walks with a velocity of 2 m/s ?
Q 46.
Two hockey players of opposite teams,while trying to.hit a hockey ball on the ground collide and immediately become entangled.One has a mass of 60 kg,and was moving with a velocity 5.0 m/s,while the other has a mass of 55 kg and was moving faster with a velocity of 6.0 m/s towards the first player,In which direction and with what velocity will they move after they become entangled ? Assume that the frictional force acting between the feet of the two players and ground is negligible.
Q 47.
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 48.
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 49.
What are balanced forces ?
Q 50.
Can balanced forces move a body at rest ?
