6 A uniform ruler AB has mass 28 g and length 30 cm. As shown in Fig. 6, the ruler is placed on a horizontal table so that it overhangs a point C at the edge of the table by 25 cm.
A downward force of \(F\) N is applied at A. This force just holds the ruler in equilibrium so that the contact force between the table and the ruler acts through C.
Fig. 6
(a) Complete the force diagram in the Printed Answer Booklet, labelling the forces and all relevant distances.[2]
(b) Calculate the value of \(F\). [2]
Mark scheme (a)
Scheme
Marks
AO
B1
B1
1.1a
1.1
[2]
Notes
B1: F and their weight even if not labelled in roughly correct position R is already drawn in Printed Answer Booklet
B1: Distances labelled. Allow for 5cm and any measurements that show that the weight is acting in the centre of the ruler.
Mark scheme (b)
Scheme
Marks
AO
Take moments about C \(10 \times 0.028g = 5F\)
M1
1.1a
\(F = 0.549\) N
A1
1.1
[2]
Notes
M1: Moments about any point with all relevant forces seen. Allow their weight and one incorrect distance [Value of R is 0.8232 N]
