Forces

Question 1

What is the difference between a vector and a scalar?

Answer 1

A vector has both magnitude and direction, while a scalar only has magnitude.

Question 2

Give three examples of vector quantities.

Answer 2

Velocity, force, acceleration.

Question 3

Give three examples of scalar quantities.

Answer 3

Speed, mass, energy.

Question 4

Why can vectors be negative but scalars cannot?

Answer 4

Vectors depend on direction, so they can have positive or negative values depending on the reference point. Scalars only represent size and cannot be negative.

Question 5

Why is velocity a vector but speed is a scalar?

Answer 5

Velocity includes both magnitude and direction, while speed only considers how fast an object moves, regardless of direction.

Question 6

Describe how a car can be accelerating even when moving at constant speed.

Answer 6

If the car moves in a circular path, its direction is constantly changing, meaning its velocity is changing, which is acceleration.

Question 7

What is a force?

Answer 7

A force is a push or pull that acts on an object due to interaction with another object.

Question 8

What are the two types of forces?

Answer 8

Contact forces (e.g., friction, normal contact force) and non-contact forces (e.g., gravitational, electrostatic, magnetic).

Question 9

Give two examples of contact forces.

Answer 9

Friction (resists motion) and normal contact force (acts perpendicular to a surface).

Question 10

Give two examples of non-contact forces.

Answer 10

Gravitational force (attraction due to mass) and electrostatic force (repulsion or attraction between charges).

Question 11

What is the equation for weight?

Answer 11

W=mg (Weight = Mass × Gravitational field strength)

Question 12

What is the value of gravitational field strength on Earth?

Answer 12

9.8 N/kg.

Question 13

How does weight change on different planets?

Answer 13

Weight depends on gravitational field strength (g), which varies from planet to planet. Mass stays the same.

Question 14

Where does the weight of an object act?

Answer 14

At its centre of mass.

Question 15

What is a resultant force?

Answer 15

The single force that represents the combined effect of multiple forces acting on an object.

Question 16

What happens if the resultant force is zero?

Answer 16

The object stays stationary or moves at constant velocity (Newton’s First Law).

Question 17

Why does a skydiver eventually stop accelerating?

Answer 17

Air resistance increases as speed increases, eventually balancing weight. This results in zero resultant force and terminal velocity.

Question 18

What is the equation for work done?

Answer 18

W=Fs (Work = Force × Distance moved in direction of force)

Question 19

What are the units of work done?

Answer 19

Joules (J).

Question 20

Why does friction increase temperature?

Answer 20

Work done against friction converts kinetic energy into heat energy.

Question 21

State Hooke’s Law.

Answer 21

Extension is directly proportional to force, provided the limit of proportionality is not exceeded.

Question 22

What is the equation for Hooke’s Law?

Answer 22

F=kx (Force = Spring constant × Extension)

Question 23

What happens if a spring is stretched beyond its limit of proportionality?

Answer 23

It undergoes plastic deformation and does not return to its original shape.

Question 24

What is the equation for a moment?

Answer 24

M=Fd (Moment = Force × Perpendicular distance from pivot)

Question 25

Give an example of a moment in everyday life.

Answer 25

Opening a door – the force applied to the handle creates a moment about the hinge.

Question 26

How can you increase the moment of a force?

Answer 26

Increase the force applied or the perpendicular distance from the pivot.

Question 27

How do levers make work easier?

Answer 27

They increase the distance from the pivot, reducing the force needed to generate the same moment.

Question 28

How does a larger gear affect force?

Answer 28

A larger gear turns slower but exerts more force than a smaller gear.

Question 29

What is the equation for pressure?

Answer 29

P=F/A (Pressure = Force ÷ Area)

Question 30

How does pressure change with depth in a liquid?

Answer 30

Pressure increases with depth due to the increasing weight of the liquid above.

Question 31

Why does a boat float?

Answer 31

If the weight of the boat is less than the weight of water displaced, the upthrust keeps it afloat.

Question 32

What does the gradient of a distance-time graph represent?

Answer 32

Speed.

Question 33

What does the gradient of a velocity-time graph represent?

Answer 33

Acceleration.

Question 34

How do you calculate acceleration?

Answer 34

a=(v−u)/t (Acceleration = Change in velocity ÷ Time)

Question 35

What is the equation of motion linking velocity, acceleration, and distance?

Answer 35

v²=u²+2as.

Question 36

State Newton’s First Law.

Answer 36

An object remains at rest or moves at a constant velocity unless acted on by a resultant force.

Question 37

State Newton’s Second Law.

Answer 37

F=ma (Force = Mass × Acceleration)

Question 38

State Newton’s Third Law.

Answer 38

Every action has an equal and opposite reaction.

Question 39

What is the equation for stopping distance?

Answer 39

Stopping Distance = Thinking Distance + Braking Distance.

Question 40

Give three factors affecting thinking distance.

Answer 40

Reaction time, speed, distractions (e.g., phone, alcohol, tiredness).

Question 41

Give three factors affecting braking distance.

Answer 41

Speed, road conditions, worn brakes or tires.

Question 42

Why do brakes heat up when stopping a vehicle?

Answer 42

Kinetic energy is converted into thermal energy due to friction in the brakes.

Question 43

What is the equation for momentum?

Answer 43

p=mv (Momentum = Mass × Velocity)

Question 44

What does it mean for momentum to be conserved?

Answer 44

Total momentum before = Total momentum after (if no external forces act).

Question 45

How do seat belts and airbags improve safety?

Answer 45

They increase the time taken for momentum to change, reducing force on passengers.