NCERT Solutions: Class 8 Science - Force and Pressure
NCERT Solutions for Class 8th Force and Pressure Science Physics
NCERT Book page 142
Question 1:
Give two examples each of situations in which you push or pull to change the state of motion of objects.
Answer 1:
1) When we pedal a bicycle more firstly it move more faster. Here pushing force change the state of motion.
2) When we apply breaks a car, it will move slowly. Here pushing force change the state of motion.
3) When we draw a bucket full water from well, here pulling force change the state of motion.
4) When we draw a drawer to open it, here pulling force change state of motion.
Question 2:
Give two examples of situations in which applied force causes a change in the shape of an object.
Answer: 1) When we apply force on a rubber ball , it’s shape change.
2) When we apply force on rubber band it’s shape is change.
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.
Answer 3:
(a)To draw water from a well we have to pull 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.
NCERT BOOK PAGE 143The
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.
Answer 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 contact force
(c) The type of force responsible for a change in the state of motion of the arrow is an example of a muscular 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.
NCERT Solutions: Class 8 Science - Force and Pressure
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 fro 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 5:
(a) (i)Agent exerting the force is fingers
(ii) the object on which the force act is lemon
(iii) the state of effect of force is shape of the lemon change.
(b) (i)Agent exerting the force is fingers
(ii) the object on which the force act is toothpaste tube.
(iii) the state of effect of force is cause of shape change of toothpaste tube.
(c) (i)Agent exerting the force is load.
(ii) the object on which the force act is spring
(iii) the state of effect of force is cause of changing shape of spring.
(d) (i)Agent exerting the force is Athlete’s muscle
(ii) the object on which the force act is athlete
(iii) the state of effect of force is cause of change in state of motion of 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?
Answer 6:
Here the muscular force of blacksmith change the shape of an object.
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?
Answer 7:
Here the electrostatic force of attraction is responsible for attraction between the balloon and the wall.
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.
Answer 8:
The force acting on a plastic bucket are: muscular force and gravitational force.
In this situation, this two forces are equal but acting in opposite direction. So they nullified each other. So no shape change occur here.
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.
Answer 9:
Two forces acting on the rocket immediately after leaving the launching pad. (i) force of gravity which try to pulls down the rocket (ii) frictional force due air which oppose the motion.
Question 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 Answer 10: The rise of water in the dropper is due to (d) atmospheric pressure.
NCERT Book page 142
Question 1:
Give two examples each of situations in which you push or pull to change the state of motion of objects.
Answer 1:
1) When we pedal a bicycle more firstly it move more faster. Here pushing force change the state of motion.
2) When we apply breaks a car, it will move slowly. Here pushing force change the state of motion.
3) When we draw a bucket full water from well, here pulling force change the state of motion.
4) When we draw a drawer to open it, here pulling force change state of motion.
Question 2:
Give two examples of situations in which applied force causes a change in the shape of an object.
Answer: 1) When we apply force on a rubber ball , it’s shape change.
2) When we apply force on rubber band it’s shape is change.
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.
Answer 3:
(a)To draw water from a well we have to pull 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.
NCERT BOOK PAGE 143The
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.
Answer 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 contact force
(c) The type of force responsible for a change in the state of motion of the arrow is an example of a muscular 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.
NCERT Solutions: Class 8 Science - Force and Pressure
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 fro 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 5:
(a) (i)Agent exerting the force is fingers
(ii) the object on which the force act is lemon
(iii) the state of effect of force is shape of the lemon change.
(b) (i)Agent exerting the force is fingers
(ii) the object on which the force act is toothpaste tube.
(iii) the state of effect of force is cause of shape change of toothpaste tube.
(c) (i)Agent exerting the force is load.
(ii) the object on which the force act is spring
(iii) the state of effect of force is cause of changing shape of spring.
(d) (i)Agent exerting the force is Athlete’s muscle
(ii) the object on which the force act is athlete
(iii) the state of effect of force is cause of change in state of motion of 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?
Answer 6:
Here the muscular force of blacksmith change the shape of an object.
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?
Answer 7:
Here the electrostatic force of attraction is responsible for attraction between the balloon and the wall.
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.
Answer 8:
The force acting on a plastic bucket are: muscular force and gravitational force.
In this situation, this two forces are equal but acting in opposite direction. So they nullified each other. So no shape change occur here.
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.
Answer 9:
Two forces acting on the rocket immediately after leaving the launching pad. (i) force of gravity which try to pulls down the rocket (ii) frictional force due air which oppose the motion.
Question 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 Answer 10: The rise of water in the dropper is due to (d) atmospheric pressure.
NCERT Solutions: Class 8 Science - Force and Pressure
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