Question:
State Newton's First Law of motion.
Answer:
Newton's First Law of motion states if a body is in state of rest, it will remain in the state of rest and if it is in the state of motion it will remain in the state of the motion with same velocity and same direction unless an external force is applied on it.
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.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 4.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 5.
Are action-reaction forces simultaneous ?
Q 6.
What is the unit of force in c.g.s system?
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.
What is the total momentum of a bullet and a gun before firing?
Q 11.
Can balanced forces change the shape and size of a body ?
Q 12.
Using second law of motion, derive the relation between force and acceleration.
Q 13.
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 14.
Explain why a player lowers his hands while catching a cricket ball.
Q 15.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 16.
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 17.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 18.
The masses of two objects are 2 kg and 20 kg. Which has greater inertia ?
Q 19.
What acceleration is produced by a force of 5 N acting on a body of mass 20 kg ?
Q 20.
A certain force exerted for 1 -2 s raises the speed of an object from 1.8 m/s to 4.2 m/s. Later,the same force is applied for 2 second. How much does the speed change in 2 s ?
Q 21.
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 22.
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 23.
What a force can do?
Q 24.
A body of mass 25 kg has momentum of 125 kg m/s. What is the velocity of the body?
Q 25.
What is the SI unit of impulse.
Q 26.
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 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.
Explain what is meant by momentum of a body.Is it a scalar or a vector ? What are its units ?
Q 29.
Derive the relation F = ma,where the symbols have their usual meanings.
Q 30.
Establish relation between inertia and mass.
Q 31.
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 32.
A bullet of mass 20 gram moving with a velocity of 300 m/s gets embedded in a freely suspended wooden block of mass 880 gram.What is the velocity acquired by the block ?
Q 33.
What are unbalanced forces ?
Q 34.
Show that kg-
and N-s represent the same quantity.Which is that quantity ?
Q 35.
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 36.
A stone of 1 kg is thrown with a velocity of 20 m s-1 across the frozen surface of a lake and comes to rest after travelling a distance of 50 m. What is the force of friction between the stone and the ice? (Calculate time taken and acceleration also).
Q 37.
If action is always equal to the reaction, explain how a horse can pull a cart.
Q 38.
Fill in the blanks :
Which has more inertia of Cricket ball or a rubber ball of the same size? __________
Q 39.
Fill in the blanks :
________ is the tendency of an object to resist a change in motion.
Q 40.
Why does a bicycle slow down when the cyclist stop pedalling?
Q 41.
How is force related to acceleration produced in a body by its application?
Q 42.
What is the SI unit of momentum?
Q 43.
What is the net momentum of gun and bullet system before firing?
Q 44.
Why does a gun recoil on firing ? Obtain an expression for recoil velocity of gun.
Q 45.
What are balanced and unbalanced forces?
Q 46.
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 47.
Name the categories of forces based on interaction.
Q 48.
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 49.
When two objects act on each other, does action-reaction force pair cancel out each other?
Q 50.
State Law of conservation of momentum.
