Chapter 5 - The Turning Effect of Forces

Question 1

How could a student check a ruler is horizontal? [1 mark]

Answer 1

• place spirit level on ruler

Question 2

State the equation linking moment, force and distance from the pivot [1 mark]

Answer 2

moment = force x distance from the pivot

Question 3

Calculate the moment of the 2N weight

State the unit.

Answer 3

2 x 60 / 2 x 0.6

= 120/1.2

= 100 N / cm

Question 4

Suggest two ways that the student could increase the moment on an object [2 marks]

Answer 4

• increase force
• increase distance of hand from pivot

Question 5

A 2N weight is placed 60cm from the pivot. The newtonmeter is placed 10cm from the pivot. Calculate the reading on the newtonmeter. Ignore the weight of the ruler (3)

Answer 5

Moment = force x perpendicular dfp

Moment = 60 x 2 = 120

clockwise moment = anticlockwise moment

120 = 10 x ans

120/10 = 12N

Question 6

The metre rule is replaced by an iron bar. The iron bar is 1 m long and has a weight of 10 N. The newtonmeter and the 2 N weight stay in their original position. Explain how this change affects the reading on the newtonmeter (3)

Answer 6

• force on newtonmeter increases
• because weight of bar has a moment
• in same direction (clockwise) as 2 N weight