Force and Motion Year 10

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Force and Motion

Year 10

N Gibellini


SLO 15/04/23

• Convert distance and time from one scale to another• Calculate speed, distance or time• Draw and interpret distance time graphs• Carry out a practical investigation with guidance• Name some simple forces and their unit of measurement• Describe the effect of balanced and unbalanced forces on an

object• Define friction and understand how it affects motion• Define “drag” and understand some basic aerodynamic principles• Describe the difference between an objects mass and its weight• Calculate weight using the formula: Weight force = mass x gravity


Unit Conversion 15/04/23


Unit Conversion 15/04/23


To work out the speed of an object you need to know:

Distance, time and speed

the distance travelled;

how long it took to travel that distance.


Average speed is calculated using this equation:

Speed can be measured in different units, e.g. m/s, km/h, km/s, miles per hour.

The units of distance and time used will give the units to be used for speed.

d

s x t

formula triangle

Calculating average speed

total distance

total timeaverage speed =


Speed formula triangle


distance (km) = speed (km/h) x time (h)

Question 1

A group set off from home and walk at an average speed of 3.6 km/h. How far would they travel in two hours?

Give your answer in km.

d

s x t

Speed calculation – question 1


Question 1

How long would it take a woman to walk 10 km if her average speed is 5.4 km/h ?

d

s x t

time =distance

speed

Speed calculation – question 1


Speed and Velocity

• An object has ___________ when it travels a ______________ in a ________ interval.

• Velocity is speed in a given ____________

• Velocity and speed are measured in metres per second (ms-1) or kilometres per hour (kmh-1)

• Speed and velocity (S or V) = Distance ÷ Time

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Your Speed

Aim: Calculate your speed

Method: Record time it takes to cover 20m

Results:

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Name Person 1 Time (sec)

Speed20/time

Person 2Time (sec)

Speed20/time

Person 3Time (sec)

Speed20/time

Walking

Hopping

Sprinting


Success Criteria

1. What is the formula for calculating speed?

2. How do you know what units are used for speed?

3. Calculate the velocity of a car that travels 200m in 20sec.

4. A large elephant carrying an oversize load travels at an average speed of 300m/s. Calculate how long it will take to complete the journey if the elephant has to travel 40m.

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Recall and use the formula for calculating speed


Results table for distance/time graph

Time/seconds Distance/metres

0

5

10

15

20

25

30

35

40

45

50

55

Car graphing activity – results table layout


Distance / Time graph for car

0

200

400

600

800

1000

1200

0 5 10 15 20 25 30 35 40 45 50 55

Time / seconds

Dis

tan

ce /

me

tre

s

The car has stopped. The graph is flat – the distance of the car from the start point is not changing.The graph is straight – there is no change in speed.

The speed of the car is changing – the graph is not flat. The slope of the graph is less steep as the car begins to slow down.

The car is starting to move. The curve shows that the speed is changing. The curve is upwards as the car accelerates at the start of the journey.

The car is going fast but at a constant speed.The graph is straight in this part of the journey.

Car graphing activity – results graph analysis


The speed of the car can be calculated by looking at the gradient of the distance/time graph.

Speed is “Distance Travelled divided by Time Taken”

These values can be read off the distance/time graph at different points, and this is the same as the gradient of the graph.

Gradient of a distance/time graph


Distance / Time graph for car

0

200

400

600

800

1000

1200

0 5 10 15 20 25 30 35 40 45 50 55

Time / seconds

Dis

tan

ce

/ m

etr

es

Consider the gradient of this graph at the point shown by the two arrows in a triangle:

The car has travelled from 200m to 800m = ______It took from 16s to 36s to travel this distance = _____

Gradient of a distance/time graph

So the speed at this point = __________________.


1. Time how long it takes you to run 100m.

Speed experiment – instructions

total distance

total timeaverage speed =

3. Repeat the experiment for each member of your group.

2. Then calculate your average speed for the run.

4. What was the fastest average speed for your group?


Name distance (m) time (s) average speed (m/s)

100

100

100

100

100

Conclusion

The fastest member of the group with an average speed of ________ was __________.

Speed experiment – results


15/04/23Distance-time graphs

40

30

20

10

0 20 40 60 80 100

4) Diagonal line

downwards =

3) Steeper diagonal line =1) Diagonal line =

2) Horizontal line =

Distance

(metres)

Time/s


Ticker Tape Practical 15/04/23


A force is a push or a pull. A force cannot be seen but you can see how a force affects an object.

What is a force?


Forces acting on an Object

• Whichever arrow is largest shows the direction of movement• Which direction has the biggest arrow?• What direction is the car moving?


Ferry forces


If the forces on an object are balanced:

If the object is stopped, _______________________

If the object is moving, then it will move at _____________.

Forces

If the forces are unbalanced:

The speed will change. (___________________)

The __________ of motion will change.

Shape of an object will change


Resultant Forces

If the:

•Forward force/thrust is greater an object will ____________

•Force of friction/drag is greater an object will __________


Success Criteria

1.Complete Worksheet Where are the forces

2.Complete Scipad pages 100

3.Give a definition of a force

4. Label the forces acting on this boat

5. Give the units used to measure force

15/04/23

Label the forces and direction of that force acting on an object


Friction always tries to slow moving object down– it _________________.

Friction is created whenever two touching objects or surfaces move past each other.

Friction also occurs when things move through air. This is called ______________________________.

Friction creates ___________________

Friction


One more? Probably the most important…

Label all sources of friction that can act on this bike.

tyre and road

brake pad and rim

wheel bearingwheel

bearing

pedal bearing

links in chain

air resistance or “drag”

What are the sources of friction?


Air resistance is a type of friction caused when objects move through the air.

400 N

300 N

Air resistance and drag

Cars are designed so that they are streamlined. The flow of air around the body is made as smooth as possible so that air resistance is minimized.

Air resistance depends on:

the ______ of the car;

the ________of the car;

the ________ of the car.


One of the most important sources of friction in cars is that between the tyres and the road.

The friction between the tyres and the road is affected by the:

inflation __________ of the tyres (flatter grip better, but uses more petrol)

road _________ better grip if rough

________________caused by the weather (rain, ice, etc) slippery when wet!

When the car brakes, the maximum possible amount of friction is desirable so that the car does not skid.

Other sources of friction in cars


15/04/23Friction

Watch the following videos and animations and answer these questions:

1)What is friction?

2)What is drag?

3)Give 2 examples where it is annoying:

4)Give 3 examples where it is useful:

5)What effect does friction have on the surfaces?

6)How can we increase friction?

7)How can we decrease friction?


Success Criteria

2. Why does a cyclist need to keep pedalling to keep a bicycle going at a steady speed?

3. What does friction always create?

4. How can you reduce drag caused by the shape of a car? Why would you want to reduce ?

5. Complete scipad pages 110-112, 114-118

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Describe factors affecting speed


Success Criteria

1. Give a definition of the following words:

Mass

Speed

Friction

Gravity

Air resistance

Drag

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Mass

• Mass is the _________ of an object, the amount of matter there is

• remains __________ (is unaffected by gravity)

• measured in ________________

• balance scales are used to compare the mass of two objects


Gravity

• Gravity is a _________ force which pulls masses (matter) together

• The bigger the masses the _______ the pull


Weight

• Weight is the force of ______________

• also known as gravity force

• measured in _________________

• varies depending on the gravitational force acting on a mass (greater the gravitational force, greater the weight)

• Measured with a ________________


Mass, Weight and Gravity

WEIGHT = ______________________________

Weight = mg g = 10 ms-2 on Earth mass = Kg . . . so when we say my weight is 65Kg we actually mean . . . If my mass is 65 Kg and I weigh (65 Kg X 10 ms-2) _______________


Weight and mass on different planets


Weight or mass?


An astronaut has a mass of 80 kg. On Earth her weight is given by:

On the Moon g = 1.7 N kg–1 and her weight is 136 N.

Her mass on the Moon is the same as it is on Earth: 80 kg.


Success Criteria 15/04/23

Describe the difference between an objects mass and its weight for road safety.Calculate weight using the formula: Weight force = mass x gravity

1. Astronauts experience ‘zero-g’ forces while in space – how much is zero-g?

2. Complete the table (g=10 on Earth, g= 0 in space, g = 4 when rocket is taking off, g = 7 on the moon)

Location Mass of Astronaut (Kg) Weight of Astronaut (N)

On Earth 64Kg

Taking Off

In Space

On the Moon


Missing words

Force and Motion Year 10

Education

time sec speed

speed method

speed aim

speed formula triangle

speed kmh x time h question

time person

distance time graphs

time draw