9702_s22_qp_11 Question 11

A horizontal wooden plank is pivoted at one end, as shown. 

The plank has a mass of 100 kg and a length of 10 m. The centre of gravity of the plank is a distance of 4 m from the pivot. 

What is the moment of the weight of the plank about the pivot? 

A 4 × 10² N m 

B 5 × 10² N m 

C 4 × 10³ N m 

D 5 × 10³ N m

ANSWER: C

The Physics Behind

• The moment of a force = force × perpendicular distance of the pivot from the line of action of the force.
• The moment of weight which is our force in this question is the product of
• mass which is 100 kg
• acceleration due to gravity 
• perpendicular distance of 4 m
• The answer therefore is C.