Sliding

Sliding

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This task is about identifying the forces at work on a slide.
girls on a slide.jpg
In the playground Moana and Julie were taking turns on the slide.  Although Julie and Moana are the same weight, Julie always managed to go down faster than Moana.

Question 2Change answer

a)  What could be two possible reasons that explain why Julie went faster?     
1.
2.

Question 2Change answer

b)  What force causes the girls to slide down?  
 
c)  What force slows the girls down?  
Task administration: 
This task can be completed with pencil and paper or online.
Copyright: 
Image: Dreamstime
Level:
4
Curriculum info: 
Science, Knowledge, Physical World
Keywords: 
physics concepts, forces, friction, gravity
Description of task: 
Students suggest why two girls of the same weight go down a slide at different speeds, and then identify the forces acting on the girls. The assessment focus is on the forces of gravity and friction.
Making Better Sense: 
Friction
Answers/responses: 
  

Y8 (10/1997)
a) Any 2 of:

  • Julie may be as 'slippery' as Moana but she could be smaller and encounter less air resistance.
  • Julie could be lying flat to reduce air resistance.
  • Julie may be wearing more 'slippery' clothes reducing the force due to friction between the two surfaces.
  • Julie may be sitting so that only a small part of her body is in contact with the slide's surface so reducing friction.
  • Julie may be using her arms to push herself down the slide/Moana might hold onto the slide to slow herself.
 2 correct – difficult

1 correct – easy
b) Gravity moderate
c) Friction very difficult

 

Diagnostic and formative information: 

 

Common errors

b)

Air/wind – 9% of students.
Slope – 6% of students.
Weight – 6% of students.
No answer – 13% students.

c)

Weight/weight of clothing – 15% of students.
Wind/air – 14% of students.
Gravity – 13% of students.
No answer – 19% of students.