0Q1: What is a force?
Answer: Force is a push or a pull acting on an object which changes or tends to change the state of the object.
Actions like pulling, pushing, lifting, kicking, opening etc. are tasks we generally do in our daily life. These actions often result in change in position of the object. We say an effort is required either to push or pull an object, this effort is called force.
The SI (International System of Units) unit of force is Newton
Q2: Give two examples of situations in which applied force causes a change in the shape of an object.
Answer:
a. A lump of dough on a plate.
b. A rubber band suspended from a hook.
Q3: Fill in the blanks in the following statements:
Answer:
(a) To draw water from a well we have to pull (force) at the rope.
(b) A charged body attracts an uncharged body towards it.
(c) To move a loaded trolley we have to push it.
(d) The north pole of a magnet repels the north pole of another magnet.
Q4: 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
Answer:
(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.
Q5: What is the relation between Force and interaction?
Answer: Whenever there is an interaction between two objects, there is a force acting upon each of the objects. When the interaction ceases, the two objects no longer experience the force. Forces only exist as a result of an interaction.
Q6: 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.
Answer:
| S. No. | Situation | Agent | Object | Effect | |
|---|---|---|---|---|---|
| 1 | Squeezing a piece of lemon between the fingers to extract its juice | Fingers | lemon | The effect of the force is that the juice is extracted from the lemon | |
| 2 | Taking out paste from a toothpaste tube. | fingers | toothpaste tube | The effect of the force is that the toothpaste is coming out from the tube | |
| 3 | A load suspended from a spring while its other end is on a hook fixed to a wall. | load | spring | The effect of the force is that the spring expands as the other end is on a hook fixed to a wall. | |
| 4 | An athlete making a high jump to clear the bar at a certain height. | athlete | athlete’s body | The effect of the body is that the athlete will jump on the other side of the bar at a certain height. |
Q7: A blacksmith hammers a piece of iron while making a tool. How does the force due to hammering affect the piece of iron?
Answer: The force due to hammering changes the shape of the piece of iron.
Q8: What force can do?
Answer: When a force is applied on an object, it:
- Can move an object from rest.
- Can change the speed of an object if it is moving.
- Can change the direction of motion of an object.
- Can bring about a change in the shape of an object.
- May or may not cause any of these or all of these effects
