# Newtons Law Points, Newton's Second Law on 20 March 2019, 10:30AM
• mass of the object
• newton laws of motion
• isaac newton
Newtons Law Key Points...

1 Rest is a natural state of an object.

2 Force is an effort which is needed to get an object into motion.

3 The S.I unit of force is kg ms-2. It is called Newton (N).

41 Newton force produces an acceleration of 1 ms-2 in a body of the mass of 1 kg.

5 We need force to change the direction of motion. We need to apply force to stop a ball moving with a high speed.

6 Force cannot change the mass of a body. It changes shape, size, velocity, and direction of motion.

7 Force can change to the magnitude of the velocity of an object.

8 The machine helps to reduce the effort or force required to do work.

9 Dyne is a CGS unit of force. 1 dyne = g cm s-2.

10 First law of motion: It states the object remains in the state of rest or in uniform motion unless an unbalanced force is applied to it.

11 If the resultant of forces applied on a body is zero, it is called balanced force. If the resultant is not zero, then the force applied is called unbalanced force.

12 Inertia is the natural tendency of the object to resist change in their state or in uniform motion.

13 Greater the inertia, more the force required to change its position or velocity, e.g. it requires a lot of effort to drive a road roller as it has more inertia.

14 The mass of an object is a measure of inertia. Greater the mass more will be inertia, more effort will be needed to move it. Its S.I unit is kg.

15 Force of friction is always opposite to motion. Vehicle stops on applying the breaks due to an increase in the force of friction.

16 The second law of motion: It states that the rate of change of momentum is directly proportional to the force applied to the object in the direction of the core. Where ‘F’ is a force, ‘m’ is mass, 'a' is acceleration.

17 The product of mass and velocity is called momentum. It is a vector quantity.

18 The direction of momentum and velocity is the same. The S.I unit of momentum is kg ms-1.

19 Third law: To every action, there is equal and opposite reaction acting on two different bodies.When we walk we apply force on the ground and frictional force acts on our body. The total momentum remains conserved in an isolated system. It is a law of conservation of momentum.

20 Friction exists between rough surfaces. It provides resistance to motion. It can be a help or a nuisance. It can be reduced by adding lubricants, graphite, water or layer of air. A direction of friction is to oppose the motion.

21 Friction is independent of the contact surface area. It is directly proportional to normal force between the surfaces.

22 Mass remains constant whereas weight depends upon the value of ‘g’, e, g, our weight will be that moon than earth due to less gravity on the moon but mass will remain same. w = mg, where ‘w’ is weight, ‘m’ is mass, ‘g’ is gravity or gravitational field strength which varies from place to place.

23 Mass and weight of an object are different.

24 SI unit of mass is kg and of weight is Newton.

25 There are three types of inertia. The inertia of rest, Inertial of motion and Inertial direction.

Newton Law Questions

### Have a look on

1 Which of the following law of conservation applicable to the motion of a rocket?

a) Conservation of mass
b) Conservation of charge

d) Conservation of energy

4 When the speed of a car is doubled, then what will be the braking force of the car to stop it in the same distance?

b) Two times
c) Half
d) One-fourth

7While catching a ball, Player pulls down his hands to lower the

a) Force

c) Impulse
d) Catching time

10 An athlete runs before a long jump to get an advantage on

b) Frictional force
c) Moment of a force
d) Principle of moments

13 A bomb at fest explodes into a large number of tiny fragments. The total momentum of all the fragment.

b) Depends on the total mass of all the fragments
c) Depends on the speeds of various fragments
d) Is infinity

16 The motion of the wheels of a bullock moving on the road is an example of

a) Oscillatory and rotator motion
b) Oscillatory and translatory motion

d) Translatory motion only

19 Law of Inertial is also known as _____.

b) Newton's second law of motion
c) Newton's third law of motion
d) None of these

22 Action and reaction ______

a) Always act on the same body

c) Are in the same direction
d) Always act independently

25 The upward force on a floating body is called ____.

a) Jerk

c) Archimedes force
d) Anti-gravity

### Most important

2 When a running car stops suddenly, the passengers tend to lean forward because of

a) Centrifugal force
b) Inertia of rest

d) Gravitational force

5 Railway tracks are banked on curves so that

a) Necessary centrifugal force may be obtained from the horizontal component of the weight of the train
b) No frictional force may be produced between the tracks and the wheels of the train

d) The train may not fall down inwards

8 A particle is moving in uniform circular motion with constant speed v along a circle of radius r. The acceleration of the particle is

a) Zero
b) v/r

d) v2/r

11The average kinetic energy of the molecules of an ideal gas is directly proportional to

a) Velocity of Molecules
b) Mass of Molecules

14Why does a cannon recoil after firing

a) Conservation of energy
b) The backward thrust of gases produced

d) Newton's first law of motion

17A person is hurt of Kicking stone due to

a) Inertia
b) Velocity

d) Momentum

20In horizontal range of a projectile is four times of its maximum height, the angle of projection is

a) 30 Degree

c) Sin -1 (3/4)
d) Sin -1 (1/4)

23If the force applied on the object is in the direction opposite to the direction of motion, the speed of the object __

a) Increases
b) Stops

d) No Effect

26What is the SI unit of Force?

a) Pascal
b) Boyle

d)Watt

### Questions

3 An object covers distance which is directly proportional to the square of time. Its acceleration is-

a) Increasing
b) Decreasing
c) Zero

6 The cause of separation of cream from milk is

a) Friction

c) Gravitational force
d) Viscous force

9 A tennis ball and a cricket ball with Heavy mass throw with the same velocity, then to stop the cricket ball we need out of the following-

b) Less force
c) Equal force
d) Infinite force

12 Why the needle of iron swims on the water surface when it is kept gently?

b) Density
c) Reaction
d) Momentum

15 The weakest of all fundamental forces are

b) Electrostatic force
c) Magnetic force
d) Nuclear force

18 A boat will not submerge when it displaces water equal to its own

b) Weight
c) Surface area
d) Density

21 The wall of a dam is broader at the base

a) Because streamlining is required

c) To withstand the pressure that increases in a horizontal plane.
d) To withstand the pressure that is increased with atmospheric pressure

24 What type of force acts on a car moving around a curve?

a) Dialysis
b) Cohesive force

d) Gravitational force

27The mass of an object _____

a) Changes from place

c) Is equal to its weight
d) Is greater at mountains