M1 June 2016 Q2

EdexcelOld spec6 marksConnected Particles Forces & Newton's Laws

Figure 1: vertical rope AB attached at B to the top of a scale pan carrying a brick — Figure 1

A vertical rope \(AB\) has its end \(B\) attached to the top of a scale pan. The scale pan has mass 0.5 kg and carries a brick of mass 1.5 kg, as shown in Figure 1. The scale pan is raised vertically upwards with constant acceleration 0.5 m s\(^{-2}\) using the rope \(AB\). The rope is modelled as a light inextensible string.

(a) Find the tension in the rope \(AB\). (3)

(b) Find the magnitude of the force exerted on the scale pan by the brick. (3)

Mark scheme (a)

Scheme	Marks
\(T - 0.5g - 1.5g = 2 \times 0.5\)	M1 A1
\(T = 20.6\) (N) or 21 (N)	A1
	(3)

Notes

N.B. In both parts of this question use the mass which is being used to guide you as to which part of the system is being considered

M1 is for an equation for whole system in \(T\) only, with usual rules

First A1 for a correct equation

Second A1 for 20.6 or 21

Mark scheme (b)

Scheme	Marks
\(R - 1.5g = 1.5 \times 0.5\)	M1 A1
Force = 15.5 (N) or 15 (N)	A1
OR: \(T - R - 0.5g = 0.5 \times 0.5\)	OR M1 A1
Force = 15.5 (N) or 15 (N)	A1
	(3)
	(6 marks)

Notes

N.B. In both parts of this question use the mass which is being used to guide you as to which part of the system is being considered

First M1 is for an equation for the brick only (1^st alternative) or for the scale pan only (2^nd alternative) with usual rules.

First A1 for a correct equation (in the second alternative \(T\) does not need to be substituted)

Second A1 for 15.5 or 15

N.B. If \(R\) is replaced by \(-R\) in either equation, can score M1A1. This would lead to \(R = -15.5\) or \(-15\). The second A1 can then only be scored if the candidate explains why the –ve sign is being ignored.