Question 1. Give two examples each of situations in which you push or pull to change the state of motion of objects
Solution 1.
Examples of situations in which you push or pull to change the state of motion of objects.
Following are the situations in which we pull to change the state of motions:
a) To open a drawer.
b) To draw water from the well, the rope is pulled
Following are the situations in which we pull to change the state of motions:
a) A football is pushed by the foot of a player.
b) pushing a heavy box in order to change its place.
Question 2. Give two examples of situations in which applied force causes a change in the shape of an object.
Solution 2. Following are the two examples of situations in which applied force causes a change in the shape of an object:
The forces which change the shape of an object are as follows:
i) Deforming the clay by pressing it between the hands.
ii) Squeezing the plastic bottle to change its shape.
Question 3. Fill in the blanks in the following statements.
(a) To draw water from a well we have to __________ at the rope.
(b) A charged body __________ an uncharged body towards it.
(c) To move a loaded trolley, we have to __________ it.
(d) The north pole of a magnet __________the north pole of another magnet.
Solution 3.
- To draw water from a well we have to pull at the rope.
- A charged body attracts an uncharged body towards it.
- To move a loaded trolley we have to pull or push
- The north pole of a magnet repels the north pole of another magnet.
Question 4. 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
Solution 4.
(a) To stretch the bow, the archer applies a force that causes a change in its shape.
(b) The force applied by the archer to stretch the bow is an example of muscular force.
(c) The type of force responsible for a change in the state of motion of the arrow is an example of a contact force.
(d) While the arrow moves towards its target, the forces acting on it are due to gravity and that due to friction of air.
Question 5. 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
Solution 5. a) we use our muscular force on the lemon by squeezing it to extract its juice. This results in a change in the shape of the lemon.
- b) we use our muscular force on the toothpaste tube to take out the paste. This results in a change in the shape of the toothpaste tube.
- c) The suspended load would exert a force on the spring and will push the spring downwards. This would result in the stretching of the spring and its shape will change.
- d) the muscular force will be exerted by the feet of the athlete on the ground, which pushes the ground. This will help him to jump over the bar—this results in a change of motion of the athlete.
Question 6. A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammering affect the piece of iron?
Solution 6. When a blacksmith hammers a hot piece of iron, he uses his muscular force on the piece of iron to give it a desirable shape.
Question 7. 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?
Solution 7. When an inflated balloon is rubbed with a piece of synthetic cloth it gets charged. Thus, it will exert an electrostatic force on the wall and will stick to it. An Electrostatic is a force where a charged body attracts the uncharged body.
Question 8. Name the forces acting on a plastic bucket containing water held above ground level in your hand. Discuss why the forces acting on the bucket do not bring a change in its state of motion.
Solution 8. The two forces that are muscular force and the gravitational force act against each other. The muscular force to hold the bucket of water above the ground acts against the force of gravity that pulls the bucket towards the ground. Thus, the two forces acting against each other the net force on the bucket becomes zero. Hence, the state of motion remains unchanged.
Question 9. A rocket has been fired upwards to launch a satellite in its orbit. Name the two forces acting on the rocket immediately after leaving the launching pad.
Solution 9. The two forces that act on the rocket immediately after leaving the launching pad are the gravitational force and the frictional force. To pull the rocket towards the ground gravitational force acts upon it. The force of friction due to the earth’s atmosphere acts against the motion of the rocket.
Question 10. When we press the bulb of a dropper with its nozzle kept in water, the air in the dropper is seen to escape in the form of bubbles. Once we release the bulb’s pressure, water fills in the dropper. The rise of water in the dropper is due to
(a) the pressure of water.
(b) the gravity of the earth.
(c) the shape of a rubber bulb.
(d) atmospheric pressure
Solution 10.
- d) atmospheric pressure