Force and pressure Worksheet-11

Force and pressure Worksheet-11

21. Is the force of gravity a contact force or non-contact force?

22. Which force is responsible for the weight of objects?

23. Does the force of gravitation exist between two objects on the earth?

24. Define pressure.

25. Do the gases and liquids exert pressure on the walls of the container?

26. Define atmosphere.

27. Why is it comfortable to lift a school bag with broad straps than thin straps?

28. Why do mountaineers suffer from nose bleeding at high altitudes?

29. Why is easier to hammer a sharp nail into wood than a blunt one?

30. How would pressure change if

(a) Area is doubled keeping force constant.

(b) Force is doubled keeping area constant?

31. Why are caterpillar tracks used in battle tanks instead of tyres?

32. Give two examples each of, situations in which you push or pull to change the state of motion of objects.

33. Give two examples of situations in which applied force causes a change in the shape of an object.

34. A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammering affect the piece of iron?

35. A camel is able to move fast on sand. Why?

36. If the force is applied opposite to the motion, what will happen to the speed of the object?

37. State the two factors which describe the state of motion of an object.

38. A stone is tied to a thread and moved in a circular path. Is any force required to do this? Is there any change in speed of the stone?

39. How do the mud particles fly off the wheel of a vehicle moving on the wet road?

40. Can muscular force be applied on an object without being directly in contact with it?

Answer:

21. Force of gravity is a non-contact force.

22. The force of gravity is responsible for the weight of objects.

23. Yes, the force of gravitation exists between two objects on the earth but it is very weak.

24. Pressure is the force acting per unit area.

25. Yes, liquids and gases exert pressure on the walls of the container.

26. The air surrounding us is known as atmosphere.

27. Pressure is inversely proportional to area. Since broader straps have greater area, therefore, the pressure decreases.

28. The atmospheric pressure decreases with high altitude. Since the pressure of the blood inside the body is high, the nose starts bleeding.

29. Pressure = force / area.

Therefore, when We hammer a sharp nail, force acts on a smaller area, and it exerts more pressure on the nail.

30. (a) If area is doubled keeping the force constant, then pressure becomes half.

(b) If force is doubled keeping area constant, then pressure becomes double.

31. Caterpillar tracks are used in battle tanks instead of tyres to increase the area of contact. As a result they can even cross sinking grounds as the pressure exerted on the ground is less.

32. Push — moving a loaded trolley and batsman hitting a ball.

Pull — opening a drawer, pulling a chair for sitting, drawing a bucket of water from a well.

33. (a) Pressing a lump of dough with hand.

(b) Pressing an inflated balloon.

34. The piece of iron becomes flattened due to the force of hammering.

35. A camel is able to move fast on sand because it has flat broad feet. This increases the area of contact and therefore, the pressure exerted by the camel on the sand reduces. Hence, the camel's feet sink very little in the sand.

36. When the force is applied opposite to the motion of the object, then either the speed decreases or the direction changes.

37. The state of motion is described by its speed and direction of motion.

38. Yes, a force is required to keep the stone moving along a circular path with a constant speed, i.e., the speed does not change.

39. The direction of the mud particles change at every point as the wheel of the vehicle moves.

40. No, muscular force can be applied only when it is in contact with an object.