Distance displacement speed and velocity.pptx

AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Distance, displacement, speed and velocity

Forces

Lesson 10 of 20

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Warm-up

Forces

Lesson 10 of 20

Answer each one, then check.

1

What is the unit of speed?

2

What is speed?

3

What is a vector?

4

What is a scalar?

5

Convert 2 minutes to seconds.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Warm-up - Answers

Forces

Lesson 10 of 20

1

What is the unit of speed?

Metres per second (m/s)

2

What is speed?

How fast something moves

3

What is a vector?

A quantity with size and direction

4

What is a scalar?

A quantity with size only

5

Convert 2 minutes to seconds.

120 s

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Learning Objectives

Forces

Lesson 10 of 20

1

Distinguish distance (scalar) from displacement (vector).

2

Distinguish speed from velocity.

3

Recall typical speeds and use a speed = distance ÷ time.

4

Recall and apply s = vt and calculate average speed.

5

Explain qualitatively that circular motion has constant speed but changing velocity (Higher tier).

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Forces

Lesson 10 of 20

SPEED AND VELOCITY

distance travelled = speed × time s = vt

Distance and speed are scalars. Displacement and velocity are vectors: velocity is speed in a given direction.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Distance and Displacement

Forces

Lesson 10 of 20

Displacement is the straight-line distance with its direction.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Typical Speeds

Forces

Lesson 10 of 20

Learn these values.

Motion

Typical speed (m/s)

Walking

1.5

Running

3

Cycling

6

Car

25

Train

55

Plane

250

Sound in air

330

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Distance from Speed

Forces

Lesson 10 of 20

A runner travels at 3.0 m/s for 2.0 minutes. How far do they run?

1

Convert time

2.0 min = 120 s

2

Substitute

s = vt = 3.0 × 120

3

Answer

s = 360 m

ANSWER

360 m

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Average Speed

Forces

Lesson 10 of 20

A cyclist travels 1500 m in 5.0 minutes. Calculate the average speed.

1

Convert time

5.0 min = 300 s

2

Rearrange

v = s ÷ t

3

Answer

v = 1500 ÷ 300 = 5.0 m/s

ANSWER

5.0 m/s

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Distance and Displacement

Forces

Lesson 10 of 20

A person walks 3 km east then 4 km north. Find the distance travelled and the displacement.

1

Distance

3 + 4 = 7 km

2

Displacement

√(3² + 4²) = 5 km

3

Direction

About 53° north of east

ANSWER

Distance 7 km; displacement 5 km at 53° north of east.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Circular Motion (Higher)

Forces

Lesson 10 of 20

A car drives round a roundabout at a constant 10 m/s. Explain whether its velocity is constant.

1

Speed

Constant at 10 m/s

2

Direction

The direction of travel keeps changing

3

Velocity

A vector, so a change in direction is a change in velocity

ANSWER

The speed is constant but the velocity changes because the direction changes.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Practical Measurement

Forces

Lesson 10 of 20

Measure speed.

Measure

Use a ruler or tape measure for distance and a stopwatch (or light gates) for time.

Average speed

Total distance divided by total time.

Non-uniform motion

Real motion rarely has constant speed, so calculate an average.

Variation

Speed depends on age, terrain, fitness and distance.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Key Terms

Forces

Lesson 10 of 20

Distance

How far an object moves; a scalar.

Displacement

Distance in a straight line from start to finish with direction; a vector.

Speed

Distance travelled per unit time; a scalar.

Velocity

Speed in a given direction; a vector.

Average speed

Total distance divided by total time.

Uniform motion

Motion at constant speed in a straight line.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Forces

Lesson 10 of 20

YOUR TASK

Journey Times

12 minutes

A car travels 120 km in 1.5 hours. Calculate its average speed in km/h and in m/s. How long would sound take to travel 660 m?

1

Convert units.

2

Use v = s ÷ t.

WHAT A GOOD ANSWER SHOWS

80 km/h; 80 ÷ 3.6 = 22 m/s. Sound: t = 660 ÷ 330 = 2.0 s.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Can I...?

Forces

Lesson 10 of 20

Define distance and displacement.

Define speed and velocity.

Use s = vt.

Calculate average speed.

Recall typical speeds.

Convert units.

Explain circular motion.

Give direction for a vector.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Summary & Exam Focus

s = vt.

Displacement and velocity are vectors.

Speed of sound in air about 330 m/s.

Circular motion: constant speed, changing velocity.

EXAM FOCUS

A runner travels at 3.0 m/s for 120 s. Calculate the distance. (2 marks)

Multiply speed by time.

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