Topic 2 - Motion and forces

Question 1

What is a scalar quantity

Answer 1

A quantity that has a magnitude (size) but no specific direction

Question 2

What is a vector quantity

Answer 2

A quantity that has both magnitude (size) and a specific direction

Question 3

What are examples of vector quantities

Answer 3

• Displacement
• Velocity
• Acceleration
• Force
• Weight
• Momentum

Question 4

What are examples of scalar quantities

Answer 4

• Distance
• Speed
• Mass
• Energy

Question 5

What is veolcity?

Answer 5

Speed in a stated direction

Question 6

What is the equation to calculate speed

Answer 6

speed = distance / time

Question 7

On a distance/time graph what value does the gradient of the line represent

Answer 7

Speed

Question 8

What is the equation for acceleration?

Answer 8

acceleration (metre per second squared, m/s^2) = change in
velocity (metre per second, m/s) ÷ time taken (second, s)

a = (v-u) / t

Question 9

How can you calculate the speed at a given time from a distance-time graph for an accelerating object

Answer 9

Draw a tangent to the curve at the required time and calculate the gradient of the tangent

Question 10

What does the gradient of a velocity/time graph represent

Answer 10

Acceleration

Question 11

How do you calculate the distance travelled by an object from a velocity-time graph

Answer 11

The area under the graph

Question 12

What are ways to measure speed

Answer 12

• Ruler and stopwatch - Ruler measures distance, stopwatch measures time taken
• Light gates - Size of object measured with a ruler, light gate connects to timer giving time taken
• Video analysis - Distance moved from frame to frame measured on ruler, time taken between frames is known

Question 13

What is average speed of running

Answer 13

3 m/s

Question 13

What is average speed of walking

Answer 13

1.5 m/s

Question 14

What is average speed of cycling

Answer 14

6 m/s

Question 15

What is average speed of a car

Answer 15

15 - 30 m/s

Question 16

What is average speed of train

Answer 16

50 m/s

Question 17

What is average speed of aeroplane

Answer 17

250 m/s

Question 18

What is typical speed of sound in air

Answer 18

330 m/s

Question 19

What is typical speed of a light breeze

Answer 19

3 m/s

Question 20

What is typical speed of a gale

Answer 20

Over 20 m/s

Question 21

What is acceleration during free fall

Answer 21

10 m/s^2

Question 22

What is Newton’s first law

Answer 22

An object remains in the same state of motion unless a resultant force acts on it

Question 23

How does newton’s first law apply for a stationary object

Answer 23

If the resultant force is 0 the object will remain at rest

Question 24

How does Newton's first law apply for a moving object

Answer 24

If the resultant force is 0 the object will remain at a constant speed

Question 25

What is newton's second law

Answer 25

Force (N) = mass (kg) x acceleration (m/s^2) F = ma

Question 26

What is weight

Answer 26

The force that acts on an object due to gravity and the object's mass

Question 27

What is the equation for weight

Answer 27

Weight (N) = mass (kg) x gravitational field strength (N/kg) W = mg

Question 28

How is weight measured

Answer 28

Using a calibrated spring-balance or newton-meter

Question 29

What is the relationship between the weight of a body and the gravitational field strength

Answer 29

As the gravitational field strength increases so does the weight if the mass remains constant

Question 30

In what situation can an object travel at a constant speed but not in a constant velocity?

Answer 30

When the object is changing direction e.g. moving in a circle

Question 31

Why does an object travelling at a constant speed in a circle not have a constant velocity

Answer 31

* Speed is a scalar quantity * Vector is a vector quantity which means that it can only be constant if the direction is constant * In a circular motion, the direction is continuously changing so the velocity is constantly changing

Question 32

What is the resultant force acting an object moving in a circle called?

Answer 32

Centripetal force

Question 33

In what direction does centripetal force act?

Answer 33

Towards the centre of the circle

Question 34

What is inertial mass

Answer 34

* A measure of how difficult it is to change the velocity of an object (including from rest) * It is the ratio of force over acceleration

Question 35

What is Newton's third law

Answer 35

Whenever two objects interact, the forces that they exert on each other are always equal and opposite

Question 36

What is the rule of conservation of momentum in collisions

Answer 36

In a closed system, the total momentum before collision is equal to the total momentum after collision

Question 37

What is the equation for momentum

Answer 37

Momentum (kg m/s) = mass (kg) x velocity (m/s) P = mv

Question 38

What is the equation linking force, change in momentum and time

Answer 38

Force = change in momentum / time F = (mv - mu) / t

Question 39

What is a way to measure human reaction times

Answer 39

Ruler drop test

Question 40

What is the stopping distance of a vehicle made up of

Answer 40

The sum of the thinking distance and braking distance

Question 41

What factors affect the stopping distance of a vehicle?

Answer 41

* The mass of a vehicle * The speed of a vehicle * The driver's reaction time * The state of the vehicle's brakes *The state of the road *The amount of friction between the tyre and the road surface

Question 42

What factors affect a driver's reaction time

Answer 42

*Tiredness *Distractions, such as phone and people in car *Drugs *Alcohol

Question 43

What is the typical range of human reaction times

Answer 43

0.3 to 0.9 seconds

Question 44

Describe the energy transfers that take place when a car applies its brakes

Answer 44

* Work is done by the friction force between the brakes and wheel * Kinetic energy of the wheel is converted to heat and is dissipated to the surroundings through the brake discs

Question 45

What are dangers caused by large decelerations?

Answer 45

*Kinetic energy converted to heat is very high causing brakes to overheat * Loss of control of the vehicle

Question 46

What happens to the braking distance of a car if its speed increases and the braking force is constant

Answer 46

The braking distance increases