Q62. If the area of my head were 10 cm × 10 cm, how much weight of air would I be carrying on my head? Why don't we feel the weight of such a huge amount of air on us?
Q63. If a vacuum is created between two Magdeburg hemispheres joined together, they cannot be separated easily. Give reason.
Why do Magdeburg hemispheres stick together?
Q64. How does a rubber sucker work?
Q65. Identify the actions involved in the following situations as push or pull, or both:
a. Opening a drawer. _______
b. A cricket ball hit by a batsman. ________
c. Drawing a bucket of water from a well. ________
d. Moving a book placed on a table. _________
e. A football player taking a penalty corner. _________
f. Moving a wheel barrow. ________
Q66. Give two examples each of situations in which you push or pull to change the state of motion of objects.
Q67. When we press the bulb of a dropper with its nozzle kept in water, air in the dropper is seen to escape in the form of bubbles. Once we release the pressure on the bulb, water gets filled in the dropper. The rise of water in the dropper is due to
(a) pressure of water
(b) gravity of the earth
(c) shape of rubber bulb
(d) atmospheric pressure.
Q68. Name the type of forces involved in the following:
a. A horse pulling a cart. ____________________
b. Moving a loaded cart. ____________________
c. A sticker attached to steel almirah without glue. __________________
d. A coin falling to the ground on slipping from hand. _________________
e. A plastic comb rubbed in dry hair picking up tiny pieces of paper. _____________________
f. A moving boat coming to rest when rowing is stopped. _______________
Q69. An inflated balloon was pressed against a wall after it has been rubbed with a piece of synthetic cloth. It was found that the balloon sticks to the wall. What force might be responsible for the attraction between the balloon and the wall?
Q70. Explain why, when a person stands on a cushion, the depression is much more than when he lies down on it.
Q71. An archer stretches her bow while taking aim at the target. She then releases the arrow, which begins to move towards the target. Based on this information fill up the gaps in the following statements using the following terms: muscular, contact, non-contact, gravity, friction, shape, attraction
(a) To stretch the bow, the archer applies a force that causes a change in its ___________.
(b) The force applied by the archer to stretch the bow is an example of ______________________ force.
(c) The type of force responsible for a change in the state of motion of the arrow is an example of a _______________ force.
(d) While the arrow moves towards its target, the forces acting on it are due to ___________ and that due to ___________ of air.
Q72. In the following situations identify the agent exerting the force and the object on which it acts. State the effect of the force in each case.
(a) Squeezing a piece of lemon between the fingers to extract its juice.
(b) Taking out paste from a toothpaste tube.
(c) A load suspended from a spring while its other end is on a hook fixed to a wall.
(d) An athlete making a high jump to clear the bar at a certain height.