Problems about deceleration

Question

two cars, A and Bhave the same velocity of 25m/s in the same direction. A is 50m behind B when the brakes are applied causing it to decelerate at a constant rate of 1.5m/s^2. when and where will A overtake B. please show the steps in solving this problem. thanks

Answer 1

Car A was heavier and had fatter tires so it stopped faster.

Answer 2

aah i think i got it:

B brakes so it decellerates towards A at 1.5m/s^2

we can take this the other way and say A accelerates towards B at 1.5m/s^2

we can take the velocity as zero because i dont see how it can make a difference what speed they are travelling at...

so s=ut+0.5*a*t^2

50=0.5*1.5*t^2

50/0.75=t^2

sqrt(50/0.75)=t

t=8.165 seconds

now to find where this happens, sub t into

s=ut+0.5*a*t^2

put the details of vehicle B in and find where it will be at this time

s=25*t+0.5*-1.5*t^2+50

add 50 because its 50m ahead of A to start with

s=204.124

now just to verify, vehicle A should have travelled the same distance after t seconds so:

8.165*25=204.124

so yup, its correct

So just note, its 204.124m ahead of where A is at the start of this, or we can say B advanced 154.124m because it started 50m ahead of A

I hope you understand what im saying, I know it isnt too clear but just message me if u need to clarify anything ;)

Answer 3

Is it Car A or B that applied the brakes? If it is A, then never. If it is B, then you will have to use simple Newtonian Physics to work it out!