Force And Pressure

Question 1

What is the unit of force?

Answer 1

Newton

Question 2

Give one example where force moves a stationary object.

Answer 2

Pushing a chair

Question 3

Give one example where force stops a moving object.

Answer 3

A fielder stopping a ball

Question 4

What is force?

Answer 4

A push or a pull on an object is called a force.

Question 5

Does liquid exert pressure in all directions?

Answer 5

Yes, Liquid exerts pressure in all directions.

Question 6

Why does the shape of the toothpaste tube change when we squeeze it?

Answer 6

The shape changes because our finger applies force on the tube.

Question 7

What can change an object’s state of motion?

Answer 7

A force may bring a change in the state of motion of an object.

Question 8

Which force can be used to gather iron pins scattered on the floor?

Answer 8

Magnetic force can be used to gather iron pins scattered on the floor.

Question 9

Which force do the animals apply while moving, chewing, and doing other activities?

Answer 9

Muscular force

Question 10

Which force is responsible for raising our body hair when we try to take off a terylene or polyester shirt in dry weather?

Answer 10

Electrostatic force

Question 11

Write one example where force changes the speed of a moving object.

Answer 11

The speed of moving a rubber tyre or a ring increases whenever it is pushed.

Question 12

Why does a boat come to rest when we stop rowing it?

Answer 12

Friction between the water and the boat brings it to a stop once we stop rowing.

Question 13

Write about two applications of atmospheric pressure in our everyday lives.

Answer 13

Drinking straws and droppers work on the existence of atmospheric pressure.

Question 14

What is pressure?

Answer 14

The force acting on a unit area of a surface is called pressure.

Pressure = force/area on which it acts

Question 15

Give one practical application of magnetic force.

Answer 15

The closing of the door of the refrigerator works on the application of magnetic forces.

Question 16

Give one example from daily life where force changes the shape of an object.

Answer 16

Example: The shape of dough changes on pressing with a rolling pin to make chapatis.

Question 17

Why do snowshoes stop you from sinking into snow?

Answer 17

The snowshoes have large, flat soles so they exert less pressure on the soft snow and stop the wearer from sinking into them.

This is due to the increased surface area of the snowshoes.

Question 18

What happens to the springs fixed to the seat of a bicycle when we sit on it?

Answer 18

The force exerted by the body weight compresses the spring and changes its shape.

Question 19

What makes a balloon get inflated when air is filled in it?

Answer 19

Air exerts pressure on the inner walls of the balloon, causing it to expand and get inflated.

Question 20

Why is a wide steel belt provided over the wheels of an army tank?

Answer 20

The wide belts increase the area and reduce the pressure, avoiding the sinking of the tank into the ground.

Question 21

Which force makes a rolling ball stop on its own?

Answer 21

It is the force of friction between the surface of the ball and the ground that brings the moving ball to rest.

Question 22

What is muscular force? Give one example.

Answer 22

The force resulting from the action of muscles is known as muscular force. Example: lifting a bucket of water.

Question 23

What is described as a change in its state of motion?

Answer 23

A change in either the speed of an object or its direction of motion, or both.

Question 24

What is meant by a contact force? Give an example.

Answer 24

A force that can be applied only when it is in contact with an object is called a contact force. Example: lifting a bucket of water.

Question 25

Why is magnetic force said to be a non-contact force?

Answer 25

A magnet can exert a force on another magnet without being in contact with it.

Question 26

Why does the shape and size of a balloon change when filled with air or water?

Answer 26

The high pressure produced by the gas or water molecules on the walls of the balloon causes it to expand and get inflated.

Question 27

What causes water to come out with more force from the downstairs tap than from the upstairs tap?

Answer 27

The pressure exerted by water increases with depth. The distance to the downstairs tap is less than to the upstairs tap.

Question 28

Why are we not crushed by atmospheric pressure?

Answer 28

Atmospheric pressure acting on our body is balanced by the blood pressure acting from inside.

Question 29

What is frictional force?

Answer 29

The force that always acts on all moving objects, opposite to the direction of motion.

Question 30

Why does a sharp knife cut better than a blunt knife?

Answer 30

A sharp knife has a lesser area, resulting in larger pressure for the same force applied.

Question 31

What is meant by atmospheric pressure?

Answer 31

The pressure exerted by the air extending up to many kilometres above the Earth's surface.

Question 32

Give two examples of contact forces.

Answer 32

* Muscular force * Frictional force

Question 33

How does hammering affect a hot piece of iron?

Answer 33

The muscular force used in hammering changes the shape of the iron.

Question 34

What is meant by a non-contact force? Give an example.

Answer 34

A force exerted by an object from a distance. Example: The force exerted by a magnet.

Question 35

What do you understand by the state of motion?

Answer 35

Described by an object's speed and direction. The state of rest is zero speed.

Question 36

Why do tools meant for cutting and piercing always have sharp edges?

Answer 36

Sharp edges concentrate force over a smaller area, making cutting easier.

Question 37

Why is the tip of a sewing needle sharp?

Answer 37

The tip of the sewing needle is sharp, so due to its sharp tip, the needle may exert force on a very small area of the cloth, producing a large pressure sufficient to pierce the fabric. ## Footnote This illustrates the principle of pressure in physics, where pressure increases as the area of contact decreases.

Question 38

What causes the speed of a ball to increase when dropped from a height?

Answer 38

The force of gravity causes all objects to fall towards the Earth, thus when a ball is dropped from a height, its speed increases gradually because of the force of gravity. ## Footnote Gravity is a fundamental force that affects all objects with mass.

Question 39

Why do porters place a thick, round piece of cloth on their heads when carrying heavy loads?

Answer 39

They increase the area of contact with the load on their head, thereby reducing the pressure on their head and making it easier to carry the load. ## Footnote This demonstrates the relationship between pressure, force, and area.

Question 40

Why are shoulder bags provided with broad straps?

Answer 40

Broad straps allow the weight of the bag to fall over a large area of the shoulder, producing less pressure on the shoulder. ## Footnote This design consideration improves comfort and reduces strain.

Question 41

What type of force is involved when a small device pulls iron nails from a distance?

Answer 41

Magnetic force is involved in this process, as the magnet exerts a magnetic force on objects made of iron, steel, nickel, and cobalt. ## Footnote Magnetic forces can act at a distance without direct contact.

Question 42

Provide one example where force changes the direction of a moving object.

Answer 42

In cricket, a batsman plays a shot by applying force on the ball with the bat, changing the speed and direction of the moving ball. ## Footnote This illustrates Newton's laws of motion, particularly the action-reaction principle.

Question 43

What can be said about the magnitudes and directions of the forces in a tug of war when the rope does not move?

Answer 43

If there is no movement on either side, the forces applied from both sides are equal in magnitude. ## Footnote This situation represents a state of equilibrium.

Question 44

Give three examples of non-contact forces.

Answer 44

The examples of non-contact forces are: * Magnetic force * Gravitational force * Electrostatic force ## Footnote Non-contact forces act at a distance and do not require physical interaction.

Question 45

What is the electrostatic force?

Answer 45

The force between charged objects due to their electric charges ## Footnote Electrostatic force can either be attractive or repulsive depending on the charges involved.

Question 46

What is the gravitational force?

Answer 46

The attractive force exerted by every object in the universe on every other object ## Footnote This force is proportional to the masses of the objects and inversely proportional to the square of the distance between their centers.

Question 47

Why is frictional force considered a contact force?

Answer 47

It arises due to contact between surfaces and always acts opposite to the direction of motion ## Footnote Frictional force is present when two surfaces interact.

Question 48

Why are the walls of a dam thicker at the bottom than at the top?

Answer 48

To withstand the greater pressure of water at greater depths ## Footnote Pressure increases with depth due to the weight of the water above.

Question 49

What are the two forces acting on a rocket immediately after leaving the launching pad?

Answer 49

The force of gravity and the force of friction due to the Earth's atmosphere ## Footnote Gravity pulls the rocket down while friction opposes its upward motion.

Question 50

Define gravitational force.

Answer 50

A force exerted by every object in the universe on every other object ## Footnote Example: Water flows towards the ground when a tap is opened.

Question 51

Give two examples of applied force causing a change in the shape of an object.

Answer 51

* The shape of the dough changes when pressed with a rolling pin * The shape of a toothpaste tube changes when squeezed ## Footnote These examples illustrate how force can deform materials.

Question 52

What are the various effects of force?

Answer 52

* It may make an object move from rest * It may change the speed of a moving object * It may change the direction of motion of an object * It may change the shape of an object ## Footnote These effects demonstrate the influence of force on physical objects.