Worked examination question Safe vehicles

a A transport engineer is investigating how the braking efficiency of a vehicle changes with different factors. Explain why one set of results showed that a van with smoother tyres took longer to stop than one whose tyres had a deeper tread. ……………………………………………………………………………………… [3] b Another set of results showed that an overloaded van took longer to stop than a correctly loaded one. The brakes were unchanged. Explain why. ……………………………………………………………………………………… ………………………………………………………………………………………[3] c Describe two ways that transport safety may be improved. ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………[4] The smooth tyres skidded instead of gripping. Force = mass  acceleration. The brakes give the same force, but the mass is bigger. Drivers need to take tests so that they can only drive alone if they are good enough. Old cars are tested each year to check they are safe on the roads. Marks 8/10 Grade = A Enough for 1 mark and a good explanation. Friction must be mentioned. Friction is less for smooth tyres than for ones with deep tread. The van stops because of the friction between tyre and road. This answer is OK for 3 marks. The student could say acceleration is less, or describe in words what is happening, but an equation with an explanation is a good way to approach these questions. Clear answers explaining why each measure works gains the student 4 marks. The student could also say that road safety signs, speed cameras, breathalysers and drug tests are another way to improve safety.

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