PHYSICS [3 Mark Question Answer]

Difference between mass and weight Mass and weight mean completely different things in physics. The amount of matter that an object contains constitutes its mass. The gravitational force acting on this mass is called the weight of the object. Mass of an object always remains the same, while the weight of the object varies when it is subjected to different gravitational forces. For example, the weight of an astronaut on the earth is six times her/his weight on the moon as the gravitational force of the earth is six times more than the gravitational force of the moon. But the body mass of the astronaut remains the same in both places.

Contact forces :

• These are forces which need a physical touch on the object to act upon it.
• These may or may not be natural forces.
• They cannot work from a distance.
• Its various types are applied force, normal force, tension, frictional force.
• Examples : Player kicking a ball, game of tug-of-war, rolling ball stops, itself, horse pulling a cart, etc.
  
  Non-contact forces :

• These are forces which do not need a physical contact to act on an object.
• These are natural forces.
• They can work from a distance as well.
• Its various types are magnetic force, electrostatic force, gravitational force.
• Examples : Magnet attracting iron nails, mango falling from tree, charged plastic ruler attracts bits of diy-paper, etc.

Various effects of force :
1. A force can move a stationary object. Example : Pulling a suitcase on its wheels.
2. A force can stop a moving object. Example : A ball rolling on rough surface comes to rest after some time due to force of friction.
3. A force can change the speed of a moving object. Example: We can increase the speed of a moving swing, we apply a force (push) in the direction of motion to increase its speed.
4. A force can change the direction of a moving object. Example: A moving bicycle changes its direction when a force is applied to steer its handle.
5. A force can change the shape and size of an object. Example: When we make a chapatti, a small ball of dough is changed to a flat, circular shape of a much bigger size by applying a force with the help of a rolling pin.