any physics person?????

Question

A certain automobile can decelerate at |a1| = 1.7 m/s2. Traveling at a constant v1 = 30 m/s, this car comes up behind a car traveling at a constant v2 = 5 m/s

How close to the slower car can the driver of the faster car come before applying his brakes and still avoid a collision?
D =______ m

Unfortunately, the driver of the faster car does not apply his brakes until he is just 30 m behind the slower car! Call the instant at which he applies the brakes t = 0.

At what time does the inevitable collision of the two cars occur?
t collision = ___s

Answer 1

I can give you a couple hints. This can seem hard because car 1 doesn't need to stop, just slow down from 30 m/s to 5 m/s. And car 2 will keep moving forward all the time. But if you see the right way to look at it, then it's easier.

Think of the back bumper of the lead car. From this viewpoint, the car is approaching at 25 m/s and has to come to 0 m/s (with respect to our new reference system). This formula should work well here:
V^2 = Vo^2 + 2as ... oops, not s, D is what you're using.

Then for the 2nd part, there's a different formula that would be best - I'm sure you have it.

Answer 2

This is sad. You can't learn if people do your homework for you. What's the benefit other than it being right?

Answer 3

Haha... Mary, I was going to say that.

Answer 4

please do your own homework.. you won't learn anything if you just ask for answers with no effort of your own..