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Home › Grade8 › Grade 8 CBSE › Physics › Force & Pressure › Force and pressure Worksheet-9

Force and pressure Worksheet-9

Force and pressure Worksheet-9

 

  1. What is muscular force? Why is it called contact force?

 

  1. What do you understand about the force of friction?

 

  1. What is electrostatic force? Why is it called non-contact force?

 

  1. Explain force of gravity.

 

  1. What is pressure? What happens to the pressure when area on which it is applied increases?

 

  1. We observe that the wheels of buses and trucks are heavier than the wheel of car or scooters. Why?

 

  1. What is atmospheric pressure?

 

  1. What are the various effects of force on different objects'?

 

  1. What are contact forces? State different contact forces.

 

  1. What are non-contact forces? Explain different types of non-contact forces.

 

  1. What is force? Name different types of forces.

 

Answer:

  1. The force resulting due to the action of muscles is called muscular force. Muscular force is called contact force because it comes in action on when two bodies come in contact of each other.

 

  1. The force which always acts on all the moving objects and whose direction is always opposite to the direction of motion is called force of friction. It arises due to contact between surfaces, so it is also called contact force.

 

  1. The force exerted by a charged body on another charged or uncharged body is called electrostatic force. This force comes into play even when the bodies are not in contact, so it is called non-contact force.

 

  1. All the objects or the things fall towards the earth because the earth pulls or attracts them. This special force or attraction of earth is called force of gravity or the force due to gravitation. It is an attractive force. This force acts on all objects.

 

  1. The force acting on a unit area of a surface is called pressure.

Pressure = Force/Area on which it acts.

The pressure is inversely proportional to the area on which force is applied. As the area on which force is increased, the pressure is decreased. We can say that pressure increases with decrease in area.

 

  1. The buses and trucks are heavy and require exerting less pressure. We know that pressure decreases as area of contact increases, so the tires are broadened so that they exert less pressure on earth and move easily. If they exert more pressure due to less broad wheels, they will sink in earth. The scooters and cars have less wide wheels because they need more pressure for gripping.

 

  1. The envelop of air around the earth is known as atmosphere. The atmospheric air extends up to many kilometers above the surface of the earth. The pressure exerted by the air is called atmospheric pressure.

 

  1. (i) May make an object move from rest.

(ii) May change the speed of moving object.

(iii) May bring about a change in the shape of an object.

(iv) May change the direction of motion of an object.

(v) May cause some or all of these effects.

 

  1. When two objects come in contact with each other then the force exerted on each other is called contact force.

(i) Muscular force: The forces resulting due the action of muscles are known as muscular forces. Muscular force is a contact force.

(ii) Force of friction: When a body is moving, then a force equal and opposite direction of motion is exerted on that moving body. This force is called force of friction. It is exerted when two surfaces come in the contact with each other.

 

  1. The forces which can be exerted from a distance, without establishing a contact are called non-contact forces. Some non-contact forces are:

(i) Magnetic force: The force exerted by a magnet on other magnet or some other magnetic substances like iron is called magnetic force. Like poles of a magnet repel each other and unlike poles of a magnet attract each other without contact..

(ii) Electrostatic force: The force exerted by a charged body on other charged or uncharged body is called electrostatic force. Electrostatic force also acts without making a direct contact with other charged or uncharged body.

(iii) Force of gravity: Earth pulls every thing or body towards it. The force of alternation exerted by earth on any object is called force of gravity.

 

  1. A push or pull on an object is called forces. There are following various types of forces:

(i) Muscular force

(ii) Force of friction

(iii) Magnetic force

(iv) Force of gravity

(v) Electrostatic force