Physics 9702 · AS & A Level · Equilibrium of forces

Equilibrium of forces — practice question

(a(i))[1]

Two forces of magnitude $5.0\,\text{N}$ and $12\,\text{N}$ act from the same point on an object. Calculate the magnitude of the resultant force $R$ when the forces are in opposite directions.

(a(ii))[1]

Two forces of magnitude $5.0\,\text{N}$ and $12\,\text{N}$ act from the same point on an object. Calculate the magnitude of the resultant force $R$ when the forces act at right angles to each other.

(b)

Object $X$ is at rest on a smooth horizontal surface. As shown in Fig. $1.1$, two horizontal forces act on $X$. One force of $55\,\text{N}$ acts to the right. A further force of $18\,\text{N}$ acts at an angle of $115^{\circ}$ to the direction of the $55\,\text{N}$ force.

(b(i))[2]

Use force resolution or a scale diagram to show that the resultant force acting on $X$ has magnitude $65\,\text{N}$.

(b(ii))[2]

Find the angle between the resultant force and the $55\,\text{N}$ force.

(c)[3]

A third force of $80\,\text{N}$ is now applied to $X$ in the direction opposite to the resultant force in (b). The mass of $X$ is $2.7\,\text{kg}$. Calculate the magnitude of the acceleration of $X$.

Worked solution & mark scheme

This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: $R = 7.0\,\text{N}$

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