Question:
Name the principle on which a rocket works.
Answer:
Newton's third law of motion.
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.
On what factor does inertia of a body depend ?
Q 3.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 4.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 5.
Are action-reaction forces simultaneous ?
Q 6.
Using second law of motion, derive the relation between force and acceleration.
Q 7.
What is the unit of force in c.g.s system?
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.
Explain why a player lowers his hands while catching a cricket ball.
Q 11.
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 12.
Can every force produce motion in every object?
Q 13.
Can balanced forces change the shape and size of a body ?
Q 14.
The masses of two objects are 2 kg and 20 kg. Which has greater inertia ?
Q 15.
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 16.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 17.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 18.
What is the total momentum of a bullet and a gun before firing?
Q 19.
What acceleration is produced by a force of 5 N acting on a body of mass 20 kg ?
Q 20.
A body of mass 25 kg has momentum of 125 kg m/s. What is the velocity of the body?
Q 21.
A truck starts from rest and rolls down a hill with a constant acceleration. It travels a distance of 400 m in 20 s. Find its acceleration. Find the force acting on it if its mass is 7 metric tonnes. (Hint: 1 metric tonne = 1000 kg.)
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.
Define 1 Newton force.
Q 24.
What is the SI unit of impulse.
Q 25.
Why mass is sometimes called coefficient of linear inertia?
Q 26.
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 27.
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 28.
In the above question,which body undergoes greater change in momentum ?
Q 29.
Explain what is meant by momentum of a body.Is it a scalar or a vector ? What are its units ?
Q 30.
State Newton’s first law of motion. Hence define force and inertia.
Q 31.
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 32.
Fill in the blanks :
On what factor does the inertia of a body depends? ____________
Q 33.
A force of 4 N acts on a body of mass 2 kg for 4 s.Assuming the body to be initially at rest,find (a) its velocity when the force stops acting (b) the distance covered in 10 s after the force starts acting.
Q 34.
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 35.
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 36.
Define momentum of a body.
Q 37.
Discuss briefly Galileo's ideas about motion.
Q 38.
Establish relation between inertia and mass.
Q 39.
State and deduce the principle of conservation of momentum.
Q 40.
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 41.
Explain why some of the leaves may get detached from a tree if we vigorously shake its branch.
Q 42.
The following is the distance-time table of an object in motion:
| Time in seconds |
Distance in meters |
| 0 |
0 |
| 1 |
1 |
| 2 |
8 |
| 3 |
27 |
| 4 |
64 |
| 5 |
125 |
| 6 |
216 |
| 7 |
343 |
(a) What conclusion can you draw about the acceleration? Is it constant, increasing, decreasing, or zero?
(b) What do you infer about the forces acting on the object?
Q 43.
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 44.
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 45.
What are unbalanced forces?
Q 46.
State Newton's third law of motion.
Q 47.
Name the principle on which a rocket works.
Q 48.
When you apply a force for a certain amount of time, it creates ________ (fill in the blank).
Q 49.
Which principle is involved in the working of a jet plane?
Q 50.
Why is the person hurt less when he falls on a spongy surface?
