Question

(a) Fig. 9.1 shows two different car tyres.

A car driver observes that her car sinks into soft ground when she uses tyres X. She changes the tyres on her car to Y, so that it does not sink into the soft ground.
Explain why tyre Y will cause less pressure to be exerted on the ground than tyre X.

(b) A thermometer is used to measure the temperature of the air in a tyre.
Fig. 9.2 shows a simple liquid-in-glass thermometer.

(i) State the name of the temperature scale used in the thermometer in Fig. 9.2.

(ii) The liquid in the thermometer is alcohol.
State the physical property of alcohol that varies with temperature used in this thermometer.

(iii) State the two physical properties that define the fixed points on this temperature scale.
1 …………………………………………………………………………
2 …………………………………………………………………………

(c) Fig. 9.3 shows two horizontal forces acting on a car as it moves along a straight road.

(i) Calculate the size and direction of the resultant horizontal force on the car.
size of resultant force = ……………………………………………………………………………….
direction of resultant force …………………………………………………………………………
(ii) The driver of the car applies the brakes to slow the car.
Fig. 9.4 shows the force from the driver’s foot on the brake pedal.

Calculate the moment of the force from the driver’s foot about the pivot.
                                        moment = ………………………………………… Ncm

▶️Answer/Explanation

Ans : 9(a) any one from greater surface area (in contact with ground) ;
same force acts over a larger area ;

9(b)(i) celsius ; 
9(b)(ii) volume ; 
9(b)(iii) melting point of ice / freezing point of water (0) ;

boiling point of water (100) ;

9(c)(i) 350 (N) ;

to the right / forward ;

9(c)(ii) moment = force × (perpendicular) distance or formula or 40 × 18 ;

= 720 (N cm) ;