This is a suggested answer to the GCE O Level Pure Physics examination, year 2015, Paper 2, Part B Question 10d.

The question provided the diagram of a skier going down the slope with the weight has one of the force acting on the skier. In the part(a) of the question, the student is required to draw and label 2 other forces acting on the skier. In part (b) of the question, it is stated that Newton’s First law of Motion describes the motion of the skier in a part of the journey. The student is required to explain using ideas about forces about what happened during that part of of the journey.

Suggested Solution

(a) The forces acting on the skier are as shown in black arrows:

 

(b) Newton’s First Law of Motion states that every object will continue in its state of rest or uniform motion in a straight line unless a resultant force acts on it to change its state. If Newton’s First Law describes that part of motion, then the skier must be moving down the slope at constant velocity, i.e, there is no acceleration. This is a situation where all the three forces are balanced and acting in equilibrium. There is therefore no resultant force that cause the skier to accelerate.