Question

a car moving with uniform acceleration haas x coordinate at 7 m at t= 0. if x coordinate at a time 4.2 sec later is -3m and at this coordinate, if it moves with a speed magnitude of 20m/s in negative x direction. find car's avg velocity, initial velocity, and acceleration.

Answer 1

Given that xo = 7m

and x = -3m

x-xo = -10m

apply v^2 = u^2+(2*a*(x-xo))

20^2 = u^2 -(2*a*10)

u^2 = 400+20a..........(1)

v = u+(a*t)

-20 = u+(a*4.2)....(2)

apply x - xo = (u*t)+(0.5*a*t^2)

-10 = (u*4.2)+(0.5*a*4.2*4.2)

-10 = 4.2*u + (8.82*a)......(3)

soliving (2) and (3) we get

-72 = 8.82*a

a = -72/8.82 = -8.2 m/s^2

initial velocity u = 14.3 m/s

avg velocity = 10/4.2 = 2.4 m/s