Science 6th grade با پاسخ UNIT 4: Forces and motion 4.7 Investigating friction
Some surfaces are more slippery than others. Why?
Activity 4.7 (How does a surface affect friction?)
You will need: a plank of wood - a pile of books - liquid soap - sand - water - a matchbox filled with sand - a shoebox - a stop watch
Set up the plank so that it makes a slope.
Put the matchbox at the top of the slope.
Measure how fast in seconds the matchbox moves down the slope.
Repeat the measurements another three times.
Record your results in a table like this one.
Wood covered in soap | Wood | Time taken for matchbox to reach ground in seconds |
reading 1 |
Cover the plank with liquid soap.
Put the matchbox at the top of the slope.
Measure how fast the matchbox moves down the slope. Repeat the measurements another three times.
Pour sand from the matchbox into a shoebox. Predict whether the shoebox will move faster down the plank than the matchbox.
Test your prediction on the dry wood and the soapy wood surfaces.
Questions
1) Compare the results for the two surfaces. On which surface did thematchbox move faster?
2) Which surface exerted the bigger frictional force? How do you know this?
3) How did the soap change the surface of the wood?
4) Why is it good to repeat measurements?
5) a Suggest a reason for your prediction. Think about which box has the bigger surface area.
b: Why did you pour the sand from the matchbox into the shoebox?
c: Suggest a reason for the results you obtained when you tested your prediction on the dry wood and soapy surfaces. Was your prediction correct?
6) Name two factors that affect frictional forces between two surfaces.