- #1

fphysicsclass

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## Homework Statement

I've already done 10 probs, but I can't figure these out. Please help if you can.

1. An automobile traveling v = 90 km/h overtakes a L = 1.00 km long train traveling in the same direction on a track parallel to the road. If the train's speed is 80 km/h, how long does it take the car to pass it, and how far will the car have traveled in this time?

x min

x km

What are the results if the car and train are traveling in opposite directions?

x s

x km

2. An unmarked police car traveling a constant 125 km/h is passed by a speeder traveling 140 km/h. Precisely 1.00 s after the speeder passes, the policeman steps on the accelerator. If the police car's acceleration is 2.50 m/s2, how much time passes after the speeder passes before the police car overtakes the speeder (assumed moving at constant speed)?

x s

## Homework Equations

dx=v(0)t+(1/2)at^2

v^2=v(0)^2+2adx

## The Attempt at a Solution

1. dx=10t? Tried making it into a rel. vel. problem.

2. (38.9)^2=(34.7)^2+2(2.5)dx ?? I've been working on this one for an hour...