NCERT Solutions Class 8 Science Chapter 11 Force And Pressure
NCERT Solutions Class 8 Science Chapter 11 Force And Pressure: National Council of Educational Research and Training Class 8 Science Chapter 11 Solutions – Force And Pressure. NCERT Solutions Class 8 Science Chapter 11 PDF Download.
NCERT Solutions Class 8 Science Chapter 11: Overview
|Force And Pressure|
NCERT Solutions Class 8 Science Chapter 11 – Force And Pressure
CHAPTER: – 11
(FORCE AND PRESSURE)
1) Give two examples each of situations in which you push or pull to change the state of motion of objects.
Ans: – The examples are
(i)In table or a wide place a ball is present and then there is push from one side it will move.
(ii)If we hand a ball through a rope and then we move it will start movement after the force is removed.
2)Give two examples of situations in which applied force causes a change in the shape of an object.
Ans:-The iron ball when hitted with the heavy force of another metal then its shape will change.
Another example is when we press any gas balloon then after sometimes it will burst.
3) Fill in the blanks in the following statements.
(a) To draw water from a well we have to ___pull____ at the rope.
Explanation- (As the water is present in the downward are so we need forces to bring it upper side)
(b) A charged body ____attract______ an uncharged body towards it.
Explanation- (It’s a property of a charged body which transfer its charges to the other body until both become same charges)
(c) To move a loaded trolley, we have to ____pull______ it.
Explanation- (There is always needed some force to overcome some frictional forces in the surface)
(d) The north pole of a magnet ___always repeals_______the north pole of another magnet.
Explanation- (The property of magnetic pole is north pole always attract the south pole and repeal the same pole)
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 __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.
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.
Ans: – The juice is stored in the lemon and when we exert pressure on it. So, in this case agent extracting the force is finger and the object is lemon.
(b) Taking out paste from a toothpaste tube.
Ans: – So, in the case of toothpaste the agent which exert pressure is the hand or fingers and the object here is toothpaste itself.
(c) A load suspended from a spring while its other end is on a hook fixed to a wall.
Ans: – Load which suspended from the spring which react as an agent which exert pressure on the spring is load and the object is spring which expands.
(d) An athlete making a high jump to clear the bar at a certain height.
Ans: – The athletes who makes the high jump is act as the agent exerting the pressure and the bar in this case is known as the object which is the barrier of the high jump case.
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?
Ans: – The hammer when is hitting with the pices of the iron then it helps in changing the shape of the iron. As the hammer when hitted on the iron the temperature produces which helps in changing the shape. At first the iron melted and the acquired its shape.
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?
Ans: – When the synthetic cloths are rubbed with the balloon and placed against the wall then a force of electrostatic is acting between them. The synthetic clothes create the electrostatic force. So, this electrostatic force helps in attached with the wall.
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.
Ans: – In this case three forces acting simultaneously one is the forces because of the water to the wall of the bucket, second the force which makes the bucket stable in hand is our force of arms and the gravitational forces on the bucket.
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.
Ans: – The forces which will be felts by the satellite in the orbit is
- The gravitational force which always trend too downward.
- The frictional force which created by the air in the going forward.
10) 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.
Ans: – Option (a) Pressure of the water.
As this pressure of the water is the main reason behind the rises in the water level in the dropper.