Pearson Edexcel International GCSE (9–1) · PHYSICS · Section
THE TURNING EFFECT OF FORCES
24 practice questions
Practice questions
1–3 of 3 · Hard
Question 1
6 marks · Hard
Answer and see the solution →A uniform metal plank of length 2.5 m and mass 4.0 kg is placed horizontally across a small stream, resting on rocks at each end (points R and S). A stone of mass 2.0 kg is placed 0.75 m from end R, as shown.
Plank and stone over stream Take gravitational field strength . Ignore the weight of the plank unless stated otherwise.
(a)[3 marks]Calculate the upward force at support S when only the stone is on the plank. (Ignore the weight of the plank.)
(b)[3 marks]Now include the weight of the plank. Calculate the new upward force at support S.
Question 2
5 marks · Hard
Answer and see the solution →A carpenter tries to lift a heavy lid off a crate using a crowbar. The crowbar is 1.2 m long. She places the fulcrum (pivot point) 0.2 m from one end. She applies a vertical downward force of 250 N at the far end of the bar (opposite the pivot).
(a)[2 marks]Calculate the moment produced by the carpenter's force about the fulcrum.
(b)[3 marks]If the lid is just lifted (i.e., the system is in balance), calculate the minimum upward force at the lid end needed to balance the moment.
Question 3
5 marks · Hard
Answer and see the solution →An athlete is balancing on a horizontal board that is supported at both ends (points L and M). The board has negligible mass. The athlete stands a distance d from support L on the 3.0 m long board. The athlete's weight is 630 N.
(a)[2 marks]Write an expression for the upward force, F_M, at support M in terms of d.
(b)[3 marks]The athlete stands 2.2 m from support L. Calculate the upward force at support M.