# Define Force and Laws of motion in Physics

Updated on Jan. 8, 2021 03:25 PM IST by Lakshmi Arya

A force is the change of state of an object due to external surroundings. Due to forces, an object will either be in a state of motion or will be resting.

we always need to apply force to make anything to move, to stop or change its direction or change the shape of an object. Like, to change the shape of a Rubber band, to knead the dough, push a trolley, stop a moving car by applying break, etc. But many times even on applying force the object does not move at all. For example- If two person push a heavy table /object from opposite sides or Two  team pull the rope with equal force in a tug of war game, we find that the table or rope does not move. When two persons push the heavy table with equal force from opposite directions, their forces get balanced, the net force on the table or rope is zero. Therefore the table or rope does not move at all. When two forces equal in magnitude are applied on an object through push or pull from opposite directions, and the resultant force on the object is zero. such force is called Balanced force. The rope or table moves only when the applied force of both persons is getting unbalanced by applying force either in the same direction or when gone of them applies more force than the other. such force is known as an unbalanced force

Few points on Force:--

1. An unbalanced force acting on an object brings it in motion.
2. To move an object the applied force must unbalance its frictional force
3. A force never acts alone. Force always exists in pairs. This pair of forces act in opposite direction. Whenever one of the  forces is greater than the other, there is a motion.
4. To accelerates the motion of an object an unbalanced force is required.

Inertia:-- The natural tendency of an object to resist a change in their state of uniform motion or of rest is called inertia.

1. Every object opposes the changes in its state of motion. It tends to remain in its state of rest or motion.
2. The mass of an object is a measure of its inertia.
3. Heavier object will have larger inertia in comparison to the lighter object, due to which we need to apply more force to change their state of motion.
Total Views: 868

### Related FAQs

Q. A ball rolled down on a floor and another on a carpet at same time, which ball comes to rest first? Give reason.

Ans: The ball on carpet comes to rest first. Because the frictional force between carpet and ball is more due to the rough surface of carpet as compared to the friction between floor and ball, So... read more

Q. Which will have more inertia: a) a car and a bus ; b) a bicycle and a motorcycle ; c) a cart and a train?

Ans: Heavier object will have more inertia in comparison to the lighter object. Therefore:- a) In a car and a bus, Bus have more inertia.   b) In a bicycle and a motorcycle, Motor cycle hav... read more

Q. In which direction, the passengers will feel the jerk, if the bus starts moving suddenly? Explain

Ans:  When a bus starts moving suddenly, the passengers will feel the jerk in backward direction. This is because the passengers tend to remain in their state of rest due to their inertia of rest.... read more

Q. Write first law of motion with example.

Ans: Newton's first law of motion states that an object at rest remains at rest and an object in motion remains in motion unless acted upon by an external force. This law is is also called law of inert... read more

Q. The velocity of an object of mass 100 kg is increased from 5 m/s to 8 m/s in 6s, find out the amount of force acting on it.

Ans: Given that :-- u = 5 m/s ,  v = 8m/s , t = 6s , m = 100kg From second law of motion :- F = m a   = m ( v - u)/t   = 100 (8 - 5)/ 6   =  50 N... read more

Q. A truck of 1000 kg mass is moving with a velocity 0.5 m/s,calculate its momentum.

Ans: Given that :-- mass (m) = 100kg  velocity (v) =0.5m/s So, momentum (p)= m×v                 = 1000×0.5           ... read more

Q. What will be the momentum of a car parked at roadside? Explain.

Ans: The momentum of a car parked at roadside will be zero, because the car is at rest so its  velocity is zero, therefore the momentum will also be zero.... read more

Q. Define momentum? Also write its S.I. unit.

Ans: Momentum is the quantity of motion possessed by a moving body, measured as a product of its mass and velocity. it is a vector quantity. its formula is given as, momentum (p) = mass(m) × velocity... read more

Q. Explain the process of walking with the help of Newton's third law of motion

Ans: When we walk, we put our foot on the ground so our foot are applying a force to it. In doing this the ground also  exerts an equal force on our foot but in opposite direction. So according to th... read more

Q. Shall we ever be able to write , if the force we apply on Pan is not reverted back by the paper, why?

Ans: No, Because according to the third law of motion ,when an object exert a  force on another object the second object also exert a force back on the first object .these two opposing forces are... read more

Q. An object of mass 0.75 kg is hanging from a string attached to roof. what will be the force applied by string on the object?

Ans: The Force applied by string on an object is  known as tension As Tension T = mg Here m is mass of object which is 0.75 kg g is the gravitational force exerted by Earth which is 9.8 Now T ... read more