Answer: Two examples in which push changes the state of motion of objects are:
• The football player kicking the football.
• The hockey player hitting the ball will hockey.
Two examples in which pull changes the state of motion of objects are:
• Pulling out water from the well by pulling rope.
• Opening of a box in the table by pulling it.
• We can change the shape of a lump of dough by pressing it down with our hands.
• We can change the shape of the seat of a bicycle by sitting on it.
1. To draw water from a well we have to ________ at the rope.
2. A charged body ________ an uncharged body towards it.
3. To move a loaded trolley we have to ________ it.
4. The north pole of a magnet ________ the north pole of another magnet.
1. To draw water from a well we have to pull at the rope.
2. A charged body attracts an uncharged body towards it.
3. To move a loaded trolley we have to pull it.
4. The north pole of a magnet repels the north pole of another magnet.
muscular, contact, non-contact, gravity, friction, shape, attraction
1. To stretch the bow, the archer applies a force that causes a change in its ________
2. The force applied by the archer to stretch the bow is an example of ________ force.
3. The type of force responsible for a change in the state of motion of the arrow is an example of a ________ force.
4. While the arrow moves towards its target, the forces acting on it are due to ________ and that due to ________ of air.
1. To stretch the bow, the archer applies a force that causes a change in its shape.
2. The force applied by the archer to stretch the bow is an example of muscular force.
3. The type of force responsible for a change in the state of motion of the arrow is an example of a contact force.
4. While the arrow moves towards its target, the forces acting on it are due to gravity and that due to friction of air.
(а) 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.
Answer: (а) The agent exerting the force is our muscles (muscular force). The force is exerted on a lemon. The effect of force is that it changes the shape of the lemon and juice is extracted.
(b) The agent exerting the force is our muscles muscular force). The force is exerted on the toothpaste tube. The effect of force is that it changes the shape of the toothpaste tube due to which paste comes out.
(c) The agent exerting the force is the load (non-contact force). The force is exerted on spring and the effect is that the spring expands.
(d) The agent exerting the force is the speed of an athlete. The force is exerted on the body of the athlete. The effect is that he can make his body jump the bar.
Answer: A blacksmith hammers a hot piece of iron while making a tool. The muscular force applied changes the shape of piece of iron. It flatters and becomes thinner than earlier.
Answer: The electrostatic force is responsible for the attraction between the balloon and the wall.
Answer: The forces acting on the bucket are:
• The pressure of water contained in it exerted on its wall and on the base of the bucket.
• Force of gravity by the earth.
The forces acting on the bucket do not bring a change in its state of motion because the net effect of force on it is zero.
Answer: The two forces that are acting on the rocket immediately after leaving the launching pad are:
• Force of gravity of earth acting downward, and
• the frictional force produced by air particles.
(a) the pressure of water.
(b) the gravity of the earth.
(c) the shape of a rubber bulb.
(d) atmospheric pressure.
(d) Atmospheric pressure
Answer: By finding the speed of both the objects.
Answer: The distance moved by an object in unit time is known as speed.
Answer: Force makes an object slow down or go faster, or change its direction of motion.
Answer: We push the football by kicking it.
Answer: To move an object, it has to be pushed or pulled.
Answer: A push or a pull on an object is called a force.
(i) Who is pushing whom
(ii) Who is pulling whom.
• In fig (a), both the girls appear to push each other i.e., they are applying force on each other.
• If fig (b) the pair of girls are trying to pull each other i.e. they are applying force on each other.
• In fig (c) the cow and the man appear to pull each other i.e., they are applying force on each other.
Fig. The rope may not move if the two teams pull at it with equal force
The rope does not move in any direction.
Answer: Forces applied on an object in the same direction add to one another.
Answer: Examples, where force can change the state of motion and direction of an object, are:
• A hockey player in-game constantly changes the state of motion and direction of the ball by hitting it with a hockey stick.
• In a game of volleyball, players often push the moving ball to their teammates to make a winning move. This changes the state of motion and direction of the ball.
Answer: Force can produce one or more effects:
• It can bring a stationary object into motion.
• It can change the speed of moving objects.
• It can change the direction of a moving object.
• It can change the shape of an object.
Answer: The force resulting due to the action of muscles is known as the muscular force.
Answer: The non-contact force acts between two objects without being in contact with each other.
Answer: The force exerted by a magnet is magnetic force.
Answer: When the same poles of two magnets are brought near each other then there is repulsion when different poles of two magnets are brought near each other then there is attraction.
Answer: The effect of a force depends on two things:
• The amount of force applied the more force applied the greater the effect.
• The area on which the force is applied the smaller the area the force is applied on, the greater the effect.
Answer: The force on a unit area (perpendicular to the surface) is called pressure.
Answer: Yes, this is due to the pressure exerted by water on the walls of the pipes.
Answer: Yes, gases exert pressure on the walls of their containers.
Answer: The envelope of air around us is called the atmosphere.
Answer: Everything around is being pressed by a column of air. This pressure is called atmospheric pressure.