Notes on using Friction1.xls

This spreadsheet allows students to explore a mathematical model of block on a rough horizontal surface being acted upon by a variable horizontal force P. The mass of the block is fixed but the value of µ can be set between 0 and 1.2.

The aim is to develop understanding of the law of friction a brief reminder of which is included in the workbook.

Background: Newton’s laws of motion and the law of friction.

Questions for students:

• Set µ equal to 0.5. Click on the animate button to see the law of friction in action.

• Use the spreadsheet to find the value of P required for limiting equilibrium.

• Verify that this is the value given by the law of friction. Describe what happens to the frictional force, the resultant force and the acceleration (i) before this point? (ii) after this point ?

• Calculate the value of the frictional force when µ = 0.8 and P = 12. Use the spreadsheet to check your answer.

• Calculate the value of the frictional force when µ = 0.8 and P = 17. Use the spreadsheet to check your answer.

• Calculate the value of the resultant force when µ = 0.4 and P = 10. Use the spreadsheet to check your answer.

• Calculate the value of the acceleration when µ = 0.6 and P = 15. Use the spreadsheet to check your answer.

• Calculate the value of the acceleration when µ = 0.8 and P = 12. Use the spreadsheet to check your answer.

• If P = 9 and there is no acceleration what can be said about µ?

• If P = 14 and there is an acceleration what can be said about µ?

• If µ = 0.2 and there is no acceleration what can be said about P?