# Now, Do You Measure Up?

In this worksheet, students will be able to concolidate their understanding of measuring accurately, equipment needed and pitfalls to be aware of.

Key stage:  KS 2

Curriculum topic:   Exam-Style Questions: SATs Science

Curriculum subtopic:   Exam-Style Questions: Measuring

Difficulty level:

### QUESTION 1 of 10

Measuring accurately is such a vital part of science - without reliable measurements, there's no useful data to learn from.

So that's why your EdPlace team is on the case and here to help you measure up!

Assuming there's a good plan in place for the investigation, then taking accurate measurements and repeating them as necessary, means that there's good data in place to use to support or challenge your hypothesis and from which to draw conclusions.

So, with all that in mind, let's join Aaron, Lily, Pradesh and Morgan as they are setting up their investigation into the speed of toy cars.

They have each chosen a toy vehicle and predicted whose will be fastest and slowest.

They have set up a track to run the cars down and set up their data logger to measure the speed of the cars.

The team looked at their cars carefully to help them predict which one they thought would be the fastest.

Which of the following variables do you think they included in helping them to make their prediction?

Colour of vehicle

Shape of vehicle

Type of suspension

Ease of rolling along

Type of wheels

Name of car

They want to know how fast each car goes - the speed.

Aaron says, "We'll need a metre ruler to measure the track and a stopwatch to time the cars."

Pradesh says, "The data logger will work that out for us."

Morgan says, "The data logger will tell us the speed, but we still need to tell it the length of the track."

Who do you think is right?

Aaron

Morgan

The four young scientists set up their car track and they position LIGHT SENSORS (called light gates), one near the top of the track (called LIGHT GATE 1) and one at the end of the track (called LIGHT GATE 2).

The light gates are connected to the datalogger.

As each car travels down the track, they break the light beam to send data to the sensor.

Place the following events in the correct order (1 for first, 2, etc. until 7):

## Column B

1
Car speeding up
2
Car starts down track
3
Car at fastest speed
4
Datalogger starts timing
5
Car breaks beam on light gate 2
6
Datalogger stops timing
7
Car breaks light beam on light gate 1

Lily cries, "Wow - that was fun! Let's do it again!"

Pradesh says, "No, it's only fair for each car to have one go each."

Aaron suggests, "But what if something went wrong on that car's run? That wouldn't be fair, would it?"

How many times do you think each car should go down the track?

1

5

20

100

On the second run for her car, Lily gave it a little push to get it started.

Why might this change the results and so not be a 'fair test'?

1

5

20

100

Aaron had used a stopwatch as well as the data logger so that they could compare the results.

They measured the track - it was 3m long

The average time his car took to run down the track was 4 seconds.

To work out the speed of the car, Aaron used this calculation:

SPEED = DISTANCE ÷ TIME

Use Aaron's results to work out the speed of his car.

1

5

20

100

What advantages and disadvantages do you think the team will have found in using a data logger rather than a stopwatch to measure the speed of their cars?

 Advantage Disadvantage More accurate Gives the speed automatically No need to do any maths Fiddly to set up

When Aaron compared the speed he'd worked out for his car (from his stopwatch) with the results from the data logger, he found that the data logger gave a faster speed for his car.

Which of the following do you think could have affected his measurements?

Reaction time (in starting/stopping the stopwatch)

He measured the whole track, not the distance between the light gates

Which car he'd chosen for the test

The results that the data logger gave them were accurate to three decimal places (3d.p.) as the young scientists had forgotten to tell the machine that they only needed the speed measurement to one decimal place (1d.p.).

Can you help them by converting their average speeds to 1d.p.?  (All the figures are in m/s)

Reaction time (in starting/stopping the stopwatch)

He measured the whole track, not the distance between the light gates

Which car he'd chosen for the test

The speeds they'd measured with the data logger were in metres per second (m/s) and they couldn't really work out whose car was the fastest just by looking at the numbers.

So, Morgan suggested that they place two metre rulers on the table and place each car where it had got to after one second.

Use that idea to place each car in order, fastest to slowest.

## Column B

Aaron = 0.8m/s
Third fastest
Lily = 1.2m/s
Slowest
Fastest
Morgan = 1.0m/s
Second fastest
• Question 1

The team looked at their cars carefully to help them predict which one they thought would be the fastest.

Which of the following variables do you think they included in helping them to make their prediction?

Shape of vehicle
Type of suspension
Ease of rolling along
Type of wheels
EDDIE SAYS
So, what makes a car faster? Colour? That fact that it's a Ford? In fact, you'll have learned that streamlining has an effect (that's its shape) as does friction (that's type of wheel and how well it rolls). Whether it has suspension or not may also have an effect. These will all have been factored into their discussion and prediction on which one they think will be the fastest.
• Question 2

They want to know how fast each car goes - the speed.

Aaron says, "We'll need a metre ruler to measure the track and a stopwatch to time the cars."

Pradesh says, "The data logger will work that out for us."

Morgan says, "The data logger will tell us the speed, but we still need to tell it the length of the track."

Who do you think is right?

Morgan
EDDIE SAYS
Although the data logger will tell the team the speed directly, they're still going to have to tell it how long the track is, otherwise, it won't be able to work out the speed of the cars.
• Question 3

The four young scientists set up their car track and they position LIGHT SENSORS (called light gates), one near the top of the track (called LIGHT GATE 1) and one at the end of the track (called LIGHT GATE 2).

The light gates are connected to the datalogger.

As each car travels down the track, they break the light beam to send data to the sensor.

Place the following events in the correct order (1 for first, 2, etc. until 7):

## Column B

1
Car starts down track
2
Car breaks light beam on light ga...
3
Datalogger starts timing
4
Car speeding up
5
Car at fastest speed
6
Car breaks beam on light gate 2
7
Datalogger stops timing
EDDIE SAYS
How did you do? It needs logical thought! They start the car and it goes whizzing down the track. It breaks the beam on light gate 1 which sends a signal to the datalogger. The car speeds up until the end of the track when it passes light gate 2 which sends a signal to the datalogger to stop timing. The machine then instantly gives a readout of the car's speed. Clever stuff!
• Question 4

Lily cries, "Wow - that was fun! Let's do it again!"

Pradesh says, "No, it's only fair for each car to have one go each."

Aaron suggests, "But what if something went wrong on that car's run? That wouldn't be fair, would it?"

How many times do you think each car should go down the track?

5
EDDIE SAYS
What do you reckon? Scientifically-speaking, the more data the better. Do you think they'd be bored before they'd done 100 goes? What about 20? That's 4 cars with 20 runs each - 80 trials. Bit much? Aaron is right - one is no good because things can easily go wrong. So, five is the best answer - enough to give useful data without being too long.
• Question 5

On the second run for her car, Lily gave it a little push to get it started.

Why might this change the results and so not be a 'fair test'?

EDDIE SAYS
A push is a forward force. The force of gravity is the only one that's meant to be moving the cars, so if Lily adds another force, they won't be able to compare the results - she'll have to do that one again!
• Question 6

Aaron had used a stopwatch as well as the data logger so that they could compare the results.

They measured the track - it was 3m long

The average time his car took to run down the track was 4 seconds.

To work out the speed of the car, Aaron used this calculation:

SPEED = DISTANCE ÷ TIME

Use Aaron's results to work out the speed of his car.

EDDIE SAYS
Hopefully, everything you needed was right in front of you. Distance is 3m. Time is 4sec. So if S=D÷T, then 3÷4 = 0.75 (or three-quarters - but you cannot write that in a maths sum!).
• Question 7

What advantages and disadvantages do you think the team will have found in using a data logger rather than a stopwatch to measure the speed of their cars?

 Advantage Disadvantage More accurate Gives the speed automatically No need to do any maths Fiddly to set up
EDDIE SAYS
Hmmm - not sure we'll all agree on this! The accuracy is good - there's no reaction time to worry about. Trouble is, it IS fiddly to set up, but once it's done you can do as many runs as you like. The fact that it gives the speed automatically (so you don't have to do any maths) may seem to be an advantage. However, it's really important to be able to do calculations without a calculator otherwise we'll lose the ability to do maths. So, although we've put that as an advantage, if you said it's a disadvantage you're not wrong and thinking ahead!
• Question 8

When Aaron compared the speed he'd worked out for his car (from his stopwatch) with the results from the data logger, he found that the data logger gave a faster speed for his car.

Which of the following do you think could have affected his measurements?

Reaction time (in starting/stopping the stopwatch)
He measured the whole track, not the distance between the light gates
EDDIE SAYS
When you use a machine which automatically measures and calculates, it's probably going to be more accurate. In this investigation, reaction time is an issue: starting the stopwatch when the car is released and stopping it when it reaches the end of the track - milliseconds are involved! If Aaron measured the whole track, and the data logger is taking the distance between the light gates (which is a shorter distance) then the results will be 'out'.
• Question 9

The results that the data logger gave them were accurate to three decimal places (3d.p.) as the young scientists had forgotten to tell the machine that they only needed the speed measurement to one decimal place (1d.p.).

Can you help them by converting their average speeds to 1d.p.?  (All the figures are in m/s)

EDDIE SAYS
Phew - did you find that tough? Some folks are great at maths and breeze through - for others, it's a battle! Basically you're looking at the number in the second decimal place and you're asking a question: is it 5 or more? So, Aaron: 0.835m/s. What's in the second decimal place? 3! Is that 5 or more? No! So, you don't add one more to the number in first decimal place, so that stays as 8. Answer = 0.8m/s. Let's do one more: What's the second decimal place for Lily? 7! Is that 5 or more? Yes! So, you add one to the number in the first decimal place. That's 1, so add another 1 and you get .... 2! Answer = 1.2m/s. Now, apply that to the other two, OK?
• Question 10

The speeds they'd measured with the data logger were in metres per second (m/s) and they couldn't really work out whose car was the fastest just by looking at the numbers.

So, Morgan suggested that they place two metre rulers on the table and place each car where it had got to after one second.

Use that idea to place each car in order, fastest to slowest.

## Column B

Aaron = 0.8m/s
Slowest
Lily = 1.2m/s
Fastest
Third fastest
Morgan = 1.0m/s
Second fastest
EDDIE SAYS
If the answers had been in mph (miles per hour) would that have been easier? Which is faster - 40mph or 60mph? Exactly the same principle applies here: how many metres can a toy car go in one second? The more, the faster. So 1.2m/s is faster than 0.8m/s. Have a think about it - you know it makes sense! Well done for working hard through this activity - hope you've been challenged!
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