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Primary Science · Year 3Chapter 9 · Forces
Year 3 Science · Forces · Lesson 9.4

Year 3 Science: Moving on different surfaces

Part of the Year 3 Science forces chapter. Chapter overview · whole chapter on one page

9.4

Moving on different surfaces

Year 3
F1: compare how things move on different surfaces, using a fair test
Story. Ruby and Aisha roll the same toy car down the same ramp, first on a smooth plastic tray, and then on sandpaper. “It goes much further on the tray,” says Aisha. Ruby says, “Let’s test it properly, so we know.”

A surface is the top layer that an object moves on, such as a floor, a carpet, a tray or a sheet of sandpaper. Different surfaces make an object move in different ways. A car on a smooth surface can roll a long way. The same car on a rough surface stops much sooner.

To compare surfaces, do a fair test. Use the same car, the same ramp, the same starting place and the same release. Change only the surface. Measure how far the car travels on each surface, and repeat each test three times.

startsurface being testeddistance travellednot to scale
A toy car rolls down a ramp and along a surface. The distance it travels on the surface is measured. Not to scale.

Ruby and Aisha recorded their results in the table. The average is the three trials added together, then divided by three.

SurfaceTrial 1 (cm)Trial 2 (cm)Trial 3 (cm)Average (cm)
Smooth plastic tray178182180180
Wooden floor149151150150
Thick carpet82788080
Sandpaper28323030
050100150average distance (cm)180 cmPlastic tray150 cmWooden floor80 cmCarpet30 cmSandpaper
The average distance on each surface, from the table: plastic tray 180 cm, wooden floor 150 cm, carpet 80 cm, sandpaper 30 cm.

Key ideas

  • Compare surfaces with a fair test: change only the surface.
  • Keep the same car, ramp, starting place and release each time.
  • Repeat each test three times, and find the average.
  • A rough surface makes the car travel a shorter distance than a smooth surface.
Worked example 9.4.1
Look at the table in section 9.4. Which surface made the car travel furthest, on average? Write the surface.

Method. Look at the averages.

  1. Find the largest average. The largest average is 180 cm, on the smooth plastic tray.
    180 cm
  2. Write the surface. So the car travelled furthest on the smooth plastic tray.
    Smooth plastic tray
  3. Write the answer.
    Smooth plastic tray

Check. The three trials on the tray were 178, 182 and 180 cm. ✓

Worked example 9.4.2
Look at the table in section 9.4. What is the average distance on the thick carpet? Write the number of centimetres.

Method. Add the three trials, then divide by three.

  1. Add the trials. The carpet trials are 82, 78 and 80 cm. Added together, they make 240 cm.
    82 + 78 + 80 = 240
  2. Divide by three. Divide 240 by 3 to get the average.
    240 divided by 3 is 80
  3. Write the answer.
    80

Check. The table shows an average of 80 cm for the carpet. ✓

Watch out. Divide by three, because there are three trials.

Worked example 9.4.3
Look at the table in section 9.4. How much further did the car travel on the smooth plastic tray than on the sandpaper, on average? Write the number of centimetres.

Method. Subtract the smaller average from the larger one.

  1. Read the two averages. The tray averages 180 cm, and the sandpaper averages 30 cm.
    180 and 30
  2. Subtract. The difference is 180 minus 30, which is 150.
    180 - 30 = 150
  3. Write the answer.
    150

Check. Check: 30 + 150 = 180. ✓

Watch out. Subtract the smaller number from the larger one.

Watch out

Watch out: if you change the car, the ramp or the release as well as the surface, the test is not fair. You will not know which change made the difference.

Try it at home or school (with a grown-up). With a grown-up, roll a toy car or a small tin down a ramp made from a book, with the other end resting on a tray. Test two surfaces: the tray and a towel. Use the same release every time. Measure how far the car goes with a ruler, three times on each surface, and find the average. Keep the ramp low, and do not roll the car near stairs or the edge of a table.

Exam tip

Grown-up tip. Ask: “What did you keep the same? Which surface made the car go furthest?” Let your child find the average by adding the three trials and dividing by three.

Exercise 9D  Moving on different surfaces

1
FLook at the bar chart in section 9.4. Which surface gives the shortest bar? Write the name.
2
FWrite the word for the top layer that an object moves on, such as a floor or a carpet.
3
FLook at the table in section 9.4. What is the average distance on the wooden floor? Write the number of centimetres.
4
FLook at the table in section 9.4. What is the average distance on the sandpaper? Write the number of centimetres.
5
FLook at the table in section 9.4. Is the average on the wooden floor more or less than the average on the thick carpet? Write more or less.
6
FFill in the gap: a rough surface makes the car travel a ___ distance. Write shorter or longer.
7
FLook at the table in section 9.4. What is the shortest of the three trials on the wooden floor? Write the number of centimetres.
8
FLook at the table in section 9.4. Add the three trials for the thick carpet. What is the total? Write the number of centimetres.
9
PSLook at the table in section 9.4. Which two surfaces have averages of more than 100 cm? Write the two names.
10
PSWorking scientifically. Predict whether the car will go further on a towel or on a wooden floor. Write towel or wooden floor, and give one reason.
11
RAli says the rougher the surface, the further the car goes. Is Ali right? Write no or yes, and give one reason.

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