An electric train of mass is moving on a straight horizontal track with a speed of
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
An electric train of mass 2.0×105kg is moving on a straight horizontal track with a speed of 18ms−1. The driver applies the brakes so that the train is brought to rest uniformly in 30s. Answer the following questions.
(i) Which category of inertia resists the stopping of the train? Give a brief reason.
(ii) Assuming the braking force acts opposite to the direction of motion and is uniform, calculate the magnitude of this net external force.
(iii) If the same magnitude of braking force were applied to a similar train whose mass is 1.0×105kg and whose initial speed is also 18ms−1, determine the time required to bring it to rest.
(iv) Using your results, comment on how the mass of a body affects the ease or difficulty with which its state of motion can be changed.