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GCSE Questions: Forces

Q10. Willow investigated how the height of a ramp affected the force needed to pull a wooden block up the ramp at a steady speed. The diagram below shows the apparatus she used.

 

(a) To pull the wooden block up the ramp Willow must do work against two forces. The force of friction is one, name the other.

The force of gravity

[1 mark]

(b)

(i) What was the independent variable in this investigation?

The height of the block

[1 mark]

(ii) What was a control variable in this investigation?

The mass of the block

[1 mark]

(c) The results from the investigation are plotted in the graph below:

 


(i) How do you know from the graph, that none of Willow's results were anomalous?

All points fit the pattern - they lie on a straight line.

[1 mark]

(ii) Use the graph to estimate the force needed to pull the wooden block along the ramp when the ramp is lying flat on the bench.

By extending the line on the graph you can see what force was needed with no incline - see the graph.

Always annotate the graph clearly so the examiner can see what you are trying to do - and what you are thinking.

1.0 N

[1 mark]

(iii) What conclusion should be made from these results?

The results show that the greater the height of the ramp the greater the force required to pull the block. This displays a positive correlation between the two.However line does not go through the origin so the relationship is not in direct proportion.

[2 marks]

(iv) Xander used the same apparatus to repeat the investigation. He increased the force of friction by fixing a rough material to the bottom of the wooden block.

Look at the graph above. Which of the result plots A, B or C is most likely to show Xander's results?

Graph C is the same as Willow's results.

Graph B is Willow's results plus a constant extra force.

Graph A is Willow's results plus an increasing extra force as the ramp gets higher.

Xander made the surface rougher - therefore the force of friction was increased by a fixed amount - so it is:

Choice B

[1 mark]

(d) The next diagram shows how a ramp is used to help move a child in a wheelchair into a car. The wheelchair is pulled up the ramp by a cable attached to an electric motor.

A force of 260 N is used to pull the child and wheelchair up the ramp. The ramp is 1.2 m long.

Calculate the work done to pull the child and wheelchair up the ramp.

Work done = force x distance moved in the direction of the force.

W = Fd

W = 260 x 1.2

W = 312 J

[3 marks]

[11 Marks TOTAL]