Question

The driver of a car slams on the brakes when he sees a tree blocking the road. The car slows uniformly with acceleration of -5.75 m/s^2 for 4.40 s, making straight skid marks 60.0 m long, all the way to the tree. With what speed does the car then strike the tree? m/s

Answer 1

0.99 m/s

Step-by-step explanation:

t = Time taken = 4.4 seconds

u = Initial velocity

v = Final velocity

s = Displacement = 60 m

a = Acceleration = -5.75 m/s²

`s=ut+(1)/(2)at^2\\\Rightarrow u=(s-(1)/(2)at^2)/(t)\\\Rightarrow u=(60-(1)/(2)* -5.75* 4.4^2)/(4.4)\\\Rightarrow u=26.29\ m/s`

`v=u+at\\\Rightarrow v=26.29+(-5.75)* 4.4\\\Rightarrow v=0.99\ m/s`

The car hits the tree at 0.99 m/s