Differentiate between contact and non contact forces . Support your answer with suitable
Answers
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Contact force :-
❝ Which results when there is a direct physical contact between two interacting objects, is known as contact force. ❞
Types :
- Muscular force
- Force of Friction
- Normal force
- Tension
➊. Muscular force
❛ The force which we exert by using our body muscles is known as muscular force. ❜
➠ In all the actions that we perform in our daily life like brushing, bathing, eating, writing, driving and walking we have to exert a force.
➠ Human beings and animals use muscular force to carry out their regular physical activities. Muscular force can be accepted only through contact.
➠ Usually we are unaware of the muscular forces that are responsible for the various actions taking place inside our body, like blood circulation, expansion and contraction of lungs during breathing, heartbeat, etc.
❷. Force of Friction
❛ Friction is a resistance to the movement of a body over the surface of another body. ❜
(or)
❛ The direction of friction is always opposite to the direction of motion relative to the surface. ❜
➠ When you roll a ball on a level ground it invariably stops after sometime.
➠ If you stop pedling your bicycle on a level road you observe that its speed decreases gradually.
❸. Normal force
❛ Direction which is perpendicular to the plane of a surface is said to be normal. ❜
(or)
❛ The force that a solid surface exerts on any object in the normal direction is called the normal force. ❜
➠ If you place a book on the table the book will fall down due to the gravitational pull of the earth. Even when your book is lying on the table the gravity pulls the book down all the time but it does not fall down because it is supported by the table. Therefore, there exists a force which supports the book against gravity by pushing it upward.
➠ In above example the downward gravitational force is balanced by the upward normal force. Since these two forces of equal magnitude and acting in opposite directions we say that the net force acting on the book is zero and the book is in equilibrium.
➍. Tension
❛ Tension is a contact force. when you try to stretch a rope or a string that tightness of rope or string is called tension. ❜
➠ A stone is suspended with the help of a string and its free end is tied to the ceiling. We know that the stone would fall down due to gravitational pull weight of the Earth of the string is broken. For a stone tied to the string, gravity pulls down the stone all the time but it does not fall down because it is supported by the string. Thus, there exist a force which supports the stone against gravity by pulling it upward.
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Non contact force :-
❝ The force which occurs without any physical contact between two objects is known as a force at a distance or field force. ❞
Types :
- Magnetic force
- Electrostatic force
- Gravitational force
➊. Magnetic force
❛ A magnet can attract or repel another magnet without contact. So magnetic force is a field force. ❜
➠ Poles of two magnets repel each other and unlike poles attract each other you can observe the red and of 11 ladle and a white and of another needle attract each other and ends with the same colour repel
➠ Now you know that like poles repel or push each other away and unlike poles attract or push each other.
This action of push or pull arises due to a magnetic force.
❷. Electrostatic force
❛ The force exerted by a charged body on another charged body is known as electrostatic force. ❜
➠ Take a balloon. Inflate it and tie up the open end. Now cut the paper into small pieces and place them on the floor. Rub the balloon with a paper and they bring the balloon near the pieces of papers.
➠ We can say that when the balloon is rubbed with a paper, it acquires an electrostatic charge on its surface. The balloon is now said to be a charged body when it is brought near the bits of paper the pieces acquire opposite charge and will rise and cling to the balloon.
❸. Gravitational force
❛ It is a force of attraction that exists between any two bodies (or masses) everywhere in the universe. ❜
➠ It is our common experience that if a pen slips off from our hands it falls down to the floor.
➠ If an object is thrown upwards, there exists a force which pulls it down towards the earth, because of this it falls down to the ground. We call this force as a gravitational force.
➠ When you sit in your classroom, there will be a gravitational force between you and your teacher, and a similar force exist between you and the black board.
➠ As the earth is so massive and huge, all the other objects close to the earth are attracted or pulled towards it.
Gravitational force works even the objects are not in contact. So this is an example of field force.
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