IB Physics SL A.2.6 Normal force

Practise finding the normal force from geometry and force components, especially for objects on slopes or surfaces at an angle.

Exam points

calculate the normal reaction on an incline using the perpendicular component of weight, often N = mg cos θ
predict how the normal force changes as slope angle increases by comparing the perpendicular component of weight

[Maximum number: 2]

This question is about the forces on a skier.

A skier is pulled up a hill by a rope at a steady velocity. The hill makes an angle of $12^{\circ}$ with the horizontal. The mass of the skier and skis is 73 kg . The diagram below shows three of the forces acting on the skier.

Figure for Question A.2.6—Normal force question 1 — IB Physics SL

Calculate the magnitude of the normal reaction acting on the skier.

$\quad(N=) m g \cos \theta /$ correct substitution;

\left(=73 \times 9.81 \times \cos 12^{\circ}=\right) 700 \mathrm{~N} ;

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A.2.6—Normal force question 1