Question

A car has a speed VA 4 m/s at point A, is moving with a constant acceleration a = 2 m/s reaches point B with VB 12 m/s. a) Calculate the time needed for the car to reach point B. b) Calculate the distance AB. c) The particle reaches point B with VB 12m/s ,moves with this speed, to reach C after 20 seconds. 1) What is with justification the nature of motion between B and C. 2) Calculate the distance BC d) At C, the driver applies a constant braking force ,in a uniformly decelerated inotion in order to stop the car at point D after 5, seconds. D Calculate the acceleration between C and D. 2) Deduce the distance CD. e) Calculate the distance AD and deduce the average speed between A and D.

Answer 1

a)

$$t=\frac{12-4}{2}=4\ s$$

b)

$$12^2-4^2=2(2)s\\s=32\ m$$

c)

$$s'=12(20)=240\ m$$

d)

$$a'=-\frac{12}{5}=-2.4\frac{m}{s^2}$$

e)

$$d=0.5(2.4)(5)^2=30\ m$$

f)

$$D=32+240+30=302\ m$$

g)

$$V=\frac{302}{4+20+5}=10.4\frac{m}{s}$$