Question

(a) Fig. 6.1 shows an athlete running on a level road.
Four forces A, B, C and D act on the runner.

Force B is the driving force which moves the athlete forward.
State the names of forces C and D.
C …………………………………………………………………………
D …………………………………………………………………………

(b) Complete the sentence to describe how forces change a body.
Forces may change the direction of motion of a body,
the …………………………………………………………………. of a body
and the …………………………………………………………………. of a body.

(c) The athlete runs up a hill at constant speed.
Use words or phrases from the list below to complete the sentences about the energy transfers taking place. Each word or phrase may be used once, more than once or not at all.

                 chemical potential                gravitational potential

                                 kinetic                      light

Stored …………………………………………………… energy from food is
transferred to …………………………………………………… energy as the athlete moves.
As the athlete moves up the hill his store of …………………………………………………… energy increases.
The speed of the athlete is constant when moving up the hill, so his …………………………………………………… energy remains constant.
(d) Explain why the athlete’s power output is greater when he runs faster.
(e) A photographer takes a photograph of the athlete using a digital camera with a thin converging lens as shown in Fig. 6.2.
Two rays of light are shown passing from the head of the athlete to the lens.

(i) A focused image of the athlete’s head is formed on the image sensor.
Complete Fig. 6.2 to show how these two rays pass from the lens to form the image on the sensor. 
(ii) On Fig. 6.2, draw a double headed arrow (↔) to show the focal length of the lens. 
(iii) Circle two words or phrases that describe the image formed.
       diminished                   enlarged            inverted

                           same size                   upright

▶️Answer/Explanation

Ans : 6(a) C weight ;
D drag / air resistance ;

6(b) Any two from size ;
shape ;
speed ;

6(c) chemical potential kinetic gravitational potential kinetic;

6(d) rate of work done increases; 
6(e)(i) ray 1 refracts through F and meets ray 2 on the image sensor ;

ray 2 continues in a straight line onto image sensor ;

6(e)(ii) focal length correctly shown ;

6(e)(iii) inverted ;
diminished ;