Force and pressure Worksheet-8

Force and pressure Worksheet-8

41. The gravitational force is contact or non-contact force.

42. Name the force due to which every object fall on earth.

43. What do you mean by pressure?

44. How we can increase the pressure by exerting same force?

45. Do liquids and gases also exert pressure?

46. What is the site of the pressure exerted by liquid on the container?

47. Do gases also exert pressure on the walls of containers?

48. What is atmosphere?

49. What is atmospheric pressure?

50. Can you separate two hemispheres, if all the air is suck out from them?

51. What is a force? Explain with the help of some examples.

52. How do we feel force in our daily life?

53. Explain that forces are due to an interaction between objects.

54. What happens when

(i) Two forces are exerted in same direction?

(ii) Two forces are exerted in opposite directions?

55. What are the two factors which affect the effect of changes?

56. What are the effect of force?

57. How can a force change the state of motion?

58. Describe state of motion.

59. What is the effect of force on the shape of an object?

60. Explain contact and non-contact forces.

Answer:

41. The gravitational force is non-contact force.

42. Gravitational force.

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

Pressure = Force/Area

44. To increase pressure we should exert the same force on smaller area.

45. Yes

46. Liquid exert pressure on the walls of the container.

47. Yes

48. The envelop of air around us is called atmosphere.

49. The pressure exerted by the air is known as atmospheric pressure.

50. There is no air inside the two hemispheres, so only outer surface is in contact of atmospheric pressure. This is because we cannot separate them.

51. Force is a pull or push of the objects. The action  like, pushing, pulling, picking, hitting, lifting, running and bending all of them are the examples of force. Push a trolly or pull a chair is force. Moving or stopping of a body like car or cycle, changing shape for example squeezing a lemon and direction of motion of objects are various actions which show force in play.

52. If we pick up something from floor

Playing catching game with ball

Playing tug of war

Pushing or pulling a chair

Pressing a balloon

53. Suppose a man is standing behind a stationary car. The car does not move due to his presence only. If the person pushes the car it means he applies a force on the car. The car may begin to move in the direction of the applied force.  So the man has to push the car to make it move. This example shows that at least two objects must interact for a force to come into play!

54. (i)When two forces are exerted in same direction on an object, then the forces are added and action becomes easy.

(i)When two forces act in the opposite directions on an object, the net force acting on it is the difference between the two forces

55. There are following two factors which affect the effect of changes.

(i) Magnitude: The strength of force is usually expressed by its magnitude.

(ii) Direction of force

If the direction or magnitude of force changes, its effect also changes.

56. A force changes or may change

(i) Speed of a moving body.

(ii) Direction of motion of a body.

(iii) Shape of a body.

57. There are two stages an object: (i) Rest and (ii) Motion.

When a force is applied on a body that it can move. In the same way a force can change the direction of moving body as well as the speed of moving body. For example if you push a ball it will start moving in the direction of force and similarly you can stop a moving ball.

If the force applied in the direction of motion, then its speed is increased if a force acts in opposite directions, then the speed of a body is decreased.

58. There are two states of motion. An object can be in two positions, one is at rest or other in motion. Any change in this position (in rest or motion) is called the change in the state of motion.

59. A force can change the shape of an object. When a force is applied on an object then change in shape takes place. It may be smaller or greater. For example rolling a chapatti from dough.

60. Contact forces: The forces which come in action only when two objects come in the contact with each other are called contact forces. Muscular force and force of friction are the examples of contact forces.

Non-contact forces: The forces which come in the action without any contact with one another are called non-contact forces. Electrostatic and magnetic forces are the examples of non-contact forces.