2.5.4 Braking distance and initial speed

Estimate how the distance required for a road vehicle to stop in an emergency varies over a range of typical speeds. • Carry out calculations on work done to show the dependence of braking distance for a vehicle on initial velocity squared (work done to bring a vehicle to rest equals its initial kinetic energy) Use of mathematics Make calculations using ratios and proportional reasoning to convert units ● rates (1c, 3c). Relate changes and differences in motion to appropriate distance-time, ● graphs, and interpret lines and slopes (4a, 4b, 4c, 4d). ● Interpret enclosed areas in velocity-time graphs (4a, 4b, 4c, 4d, ● Apply formulae relating distance, time and speed, for uniform motion, uniform acceleration, and calculate average speed for non-uniform motion ● Estimate how the distances required for road vehicles to stop in an emergency, over a range of typical speeds (1c, 1d, 2c, 2h, 3b, 3c). ● Apply formulae relating force, mass and relevant physical constants, including gravitational field strength, to explore how changes in these are inter-related ● Apply formulae relating force, mass, velocity and acceleration to explain involved are inter-related (3b, 3c, 3d). ● Estimate, for everyday road transport, the speed, accelerations and forces large accelerations (1d, 2b, 2h, 3c). Suggested practicals g, ● Investigate the acceleration, in free fall and the magnitudes of everyday ● Investigate conservation of momentum during collisions. Investigate inelastic collisions with the two objects remaining together ● and also ‘near’ elastic collisions. Investigate the relationship between mass and weight. ● ● Investigate how crumple zones can be used to reduce the forces in collisions.