Question

(a) (i) Fig. 3.1 shows a skier standing on the snow.

When she stands on the snow without her skis, she sinks into the snow.
When she wears her skis, she can stand on the snow without sinking.
Explain these observations.

(ii) The skier makes a sound near a high wall.
The sound travels through the air as a wave.
The skier hears an echo.
State what happens to the sound wave at the high wall to cause an echo to be heard.

(b) Fig. 3.2 shows the forces acting on the skier on level snow when she is travelling in a snowmobile.

(i) State which force, J, K, L or M, is the weight of the snowmobile and skier.
(ii) State which force, J, K, L or M, is the friction force acting on the snowmobile.

(c) Fig. 3.3 shows the speed–time graph for the motion of the skier.

(i) State the maximum speed of the skier.
                                    speed = …………………………………………. m / s 
(ii) The skier is accelerating during the first 20 s of her journey.
Describe how the graph shows that the skier is accelerating.
(iii) Show that the distance travelled by the skier during the first 20 s is 50 m.
(d) The skier is exposed to ultraviolet radiation from the Sun.
Ultraviolet radiation is a form of ionising radiation.
Describe one danger to humans of being exposed to large quantities of ultraviolet radiation.