Brake a car from 85km/h to 35km/h over a displacement of 100m. a) What is the acceleration? Assume it to be constant.
b) What is the interval time?
c) If continue with acceleration in (a) to slow
down until the car is rest, what is the elapsed time?
d) draw a displacement Vs time graph for the situation
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Aparticle's position is given by x = 3.00 - 9.00t + 3t2, in which x is in meters and t is in seconds. (a) what is its velocity at t = 1 s? (b) is it moving in the positive or negative direction of x just then? (c) what is its speed just then? (d) is the speed increasing or decreasing just then? (try answering the next two questions without further calculation.) (e) is there ever an instant when the velocity is zero? if so, give the time t; if not, answer "0". (f) is there a time after t = 3 s when the particle is moving in the negative direction of x? if so, give the time t; if not, answer "0".