# Homework Help: Velocity and acceleration

1. Feb 24, 2012

Hello,

Would somebody be able to explain to me how to calculate the answer to this question? I'm studying for an exam and cannot figure it out.

Question:

The rear of a bicycle passes a point O on a road with a velocity 4 ms-1 and an acceleration of 2 ms-2. Four seconds later the front of a car passes O with a velocity of 2 ms-1 and acceleration of 4 ms-2. When and how far from O does the front of the car meet the rear of the bicycle?

Many thanks

John

2. Feb 24, 2012

### Integral

Staff Emeritus
You will need to show us some of your thoughts and effort before we can help.

3. Feb 24, 2012

Hello,

This is what I think, but I can't seem to get the correct answer.

s1 = 4t + 0.5(2)t^2 distance bike goes
s2 = 2(t-4) + 0.5(4)(t-4)^2 distance car goes

then set s1 = s2 and solve

the answer is 16.5 seconds but I can't get this. maybe it is my algebra!

Thank you

4. Feb 24, 2012

### SammyS

Staff Emeritus
That's the correct method.

Show how you solve for t.

5. Feb 24, 2012

I solved it and got the correct answer.

Originally I was using (t+4)

Could you explain to me why it is (t-4) and not (t+4)? What is reasoning behind it?

Thank you

6. Feb 24, 2012

### vivekrai

It depends on for which motion do you take the time to be ' t '. See how does it make a difference?