# Motion problem for constant acceleration

1. Sep 20, 2010

### chroncile

1. The problem statement, all variables and given/known data
A pedestrian is running at his maximum speed of 6.0 m/s trying to catch a bus that is stopped at a traffic light. When he is at 16 m from the bus, the light changes and the bus pulls away from the pedestrian with an acceleration of 1.0 m/s2.

Does the pedestrian catch the bus and, if so, how far does he have to run? (If not, what is the pedestrian's distance of the closest approach?)

2. Relevant equations
d = vi * t + 0.5 * a * t2

3. The attempt at a solution
I don't understand how to do it

2. Sep 20, 2010

### collinsmark

Show us your best try. What is your equation for the displacement of the bus, from the traffic light, as a function of time t? What is your equation for the pedestrian's displacement from the traffic light as a function of time t? Is there ever a real-valued, positive time t where the displacements are equal?

Hint: there's a more general equation that you might consider using, instead of the one you quoted (and don't forget the bus and the pedestrian each have their own individual velocities and accelerations):

d = di + vit + ½at2