3B1 Force their applications

Question 1

What is force in simple terms?

Answer 1

An external agent that changes the state of rest or motion, direction, shape, or size of an object.

Question 2

What is an applied force?

Answer 2

A push or pull exerted by one object on another.

Question 3

Give an example of applied force.

Answer 3

• A person pushing a door open.
• A person pulling a suitcase on wheels.

Question 4

How can an applied force affect an object?

Answer 4

It can change:

• the state of rest or motion
• direction
• shape
• size of the object

Question 5

What are the characteristics of applied force?

Answer 5

• It results from interaction between objects.
• Has magnitude and direction.
• Can change the object’s state or shape.

Question 6

What is meant by contact force?

Answer 6

A force that occurs when two objects are in physical contact.

Question 7

What is a non-contact force?

Answer 7

A force exerted by an object on another without physical contact.

Question 8

Give an example of a non-contact force.

Answer 8

• The gravitational pull of the Earth on objects.
• A magnet attracting metal object at some distance.

Question 9

What is meant by ‘applied forces are vectors’?

Answer 9

Applied forces have both magnitude and direction.

Examples include force, velocity, and acceleration.

Question 10

Explain what it means when we say that ‘applied forces are additive in nature’.

Answer 10

This means that when more than one force acts on an object, the resultant force is given by the vector sum of the individual forces.

For example, if two people push a box in the same direction with forces of 5N and 10N, the resultant force is 15N in that direction.

Question 11

What happens when two equal forces act in opposite directions on an object?

Answer 11

The resultant force is zero.

Question 12

List some examples of contact forces.

Answer 12

• Friction
• Air resistance
• Tension force
• Spring force

Question 13

List some examples of non-contact forces.

Answer 13

• Gravitational force
• Electrostatic force
• Magnetic force

Question 14

Calculate the resultant force on the object in the diagram.

Answer 14

5N - 5N = 0N

The resultant force is found by subtracting the opposing forces.

If forces are in opposite directions, you subtract their magnitudes. If they are in the same direction, you add them.

Question 15

What is friction?

Answer 15

The force that arises when two surfaces rub over each other.

Friction always acts in the direction opposite to the motion, reducing the speed of moving objects.

Question 16

What is air resistance?

Answer 16

A type of frictional force that acts on objects as they move through air.

Air resistance increases with the speed of the moving object and the surface area of the object.

Question 17

Which force is acting on the rope that is being pulled on both sides?

Answer 17

Tension

Tension is the force transmitted through a string, rope, cable, or similar object when it is pulled tight by forces acting from opposite ends.

Question 18

Which force is acting on the compressed spring?

Answer 18

Spring force

Spring force obeys Hooke’s Law, which states that the force exerted by a spring is directly proportional to its displacement from the equilibrium position.

Question 19

What is electrostatic force?

Answer 19

The force between stationary electric charges.

Question 20

How does gravitational force affect Earth and the Solar System?

Answer 20

It keeps planets revolving around the sun and objects stuck to Earth.

Question 21

How does Earth’s gravity affect objects?

Answer 21

Gravity is a force that pulls objects toward the Earth’s center, giving them weight.

Weight is different from mass; weight is the force exerted by gravity on an object, while mass is the amount of matter in the object.

Question 22

How does a non-contact magnetic force work in a refrigerator?

Answer 22

A magnetic strip on the door attracts the metallic body of the refrigerator, closing it.

Question 23

How can applied forces be categorized?

Answer 23

• Contact forces
• Non-contact forces

Question 24

How can applied forces change an object’s motion?

Answer 24

By altering its speed or direction.

Newton’s First Law states that an object will remain at rest or in uniform motion unless acted upon by an external force.

Question 25

How does a baseball player apply force to the ball?

Answer 25

By hitting it, changing its direction of motion.

Question 26

What force acts on a ball when caught by a football player?

Answer 26

The applied force stops the ball’s motion.

Question 27

How do contact forces differ from non-contact forces in terms of distance?

Answer 27

• Contact forces act with zero distance between objects.
• Non-contact forces act over a distance.

Question 28

What type of force is involved in pushing a heavy parcel?

Answer 28

Both contact (push) and non-contact (gravitational) forces.

Question 29

What are forces measured in?

Answer 29

Newtons (N)

Question 30

Explain how weight is a force.

Answer 30

It is the force exerted by gravity on an object’s mass, and it always acts downwards.

The weight of an object can be calculated by multiplying its mass (in kilograms) by the acceleration due to gravity (approximately 9.8 m/s² on Earth).

Question 31

How do you determine the resultant force when multiple forces act on an object?

Answer 31

By calculating the vector sum of all individual forces acting on the object.

This involves adding forces that act in the same direction and subtracting forces that act in opposite directions.

Question 32

What are balanced forces?

Answer 32

They are equal in magnitude and opposite in direction, keeping an object at rest or maintaining its constant velocity.

Question 33

What are unbalanced forces?

Answer 33

They are forces in opposite directions that are not equal, causing an object to change velocity.