Question

A speeder traveling at a constant speed of
81 km/h races past a billboard. A patrol car
pursues from rest with constant acceleration
of (7 km/h)/s until it reaches its maximum
speed of 124 km/h, which it maintains until it
catches up with the speeder.
How long does it take the patrol car to
catch the speeder if it starts moving just as
the speeder passes?
Answer in units of s

How far does each car travel?
Answer in units of km

Answer 1

Probably make things easier to convert hours to seconds to keep units consistent.

Answer 2

okay

Answer 3

Also: Always draw a picture.

Answer 4

so km/h to m/s

Answer 5

woah

Answer 6

Set up kinematics equations for both, then set distance for each equal to each other.

Answer 7

You can probably leave km as km since it wants the answer in those units.

Answer 8

But it wants time solved in terms of seconds, so might as well make that conversion now (or not, you can do it later too).

Answer 9

yea but it says Answer in units of km

Answer 10

Yes. That's why I said change hours to seconds, but leave km alone.

Answer 11

alright

Answer 12

So what are your first two equations?

Answer 13

7km/h/s=1.94444444 m / s2

Answer 14

124-81/7

Answer 15

right

Answer 16

Ermmm, not sure if that's it.
Try this:
The speeder is at constant velocity, so that's a simple distance = velocity × time situation.
The patrol car is accelerating constantly until a final velocity, so you'll first have to find the distance and time involved in that accelerated part.