This GCSE Physics quiz explores forces and braking, including stopping distances, thinking time, and the factors that affect how safely vehicles can slow down and stop.
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You can find more about this topic by visiting BBC Bitesize - Motion of vehicles
Whenever forces are in equilibrium, motion is either unchanging or the object is stationary
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Some questions regarding braking can be answered by using nothing more complicated than simple ratios to calculate distances
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The driver needs to push the brake pedal harder. This could lead to the dangerous situation where the force of braking locks up the wheels. When this happens, the driver has little control over the vehicle. To avoid this danger, most vehicles are now equipped with anti-locking braking systems
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Faster speeds mean greater braking distances are required. Careful drivers therefore leave more of a gap between their vehicle and the one in front at higher speeds
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The stopping distance is the distance the car will travel in total. This takes into consideration how long it takes a driver to react to a situation and consequently the distance travelled during this period. It also takes into consideration the distance the car takes to stop once the brakes have been applied
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At a speed of 10 m/s, the car travels one metre every 0.1 second. With a thinking time of 0.2 seconds, the car will therefore have travelled 2 metres.
You have the initial speed of the car before braking, the final speed after braking (must be 0 m/s since it has stopped) and the time it took to stop the car. You can therefore use the equation s = ½ (v+u) × t to calculate the stopping distance. This is then added to the distance travelled during the thinking time to come up with the answer. You could also use s = ut + ½ at2 but you would then need to take the additional step of calculating the acceleration. Make sure that you learn the equations of motion linking initial velocity (u), final velocity (v), acceleration (a), displacement (s) and time (t). |
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The other factor is distraction - talking to passengers, using their mobile phone, loud music and so on
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Energy can only be transferred, so the kinetic energy of the car needs to be transferred into another form - in this case the heat in the brakes
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Braking distance can be severely reduced by any of the above which is why it is important to regularly check for brake and tyre wear. It is also important to leave a larger gap between cars in poorer weather conditions. Speed also affects the braking distance so it is also important to leave a larger gap between cars moving at high speeds
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This is created as the vehicle collides with air molecules
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