a sprinter accelerates from rest to a top speed with an acceleration whose magnitude is 3.8m/s². after achieving top speed, he runs the remainder of the race without speeding up or slowing down. the total race is fifty metres long. if the total race is run in 7.88 s, how far does he run during the acceleration phase?

Looks like homework to me.

I always take a sheet of paper,a pencil, and put the question into a small diagram, that helps a lot.

Looks like homework to me.

I always take a sheet of paper,a pencil, and put the question into a small diagram, that helps a lot.

 

yeeh i tried that, my teacher said the answer is found using quadratics.

 

 

 

use all the equations of motion.

yeeh i tried that, (...).

 

Obviously, that didn't help.

where is your problem?

1. understanding the parameters of the question?

2. which equations to use?

3. or the resolution (the math)?

Perhaps you should write down the equations of motion that you know - and see how they apply to your question. Bear in mind that you might have a situation that has a period of uniform acceleration followed by a period of uniform velocity. Michel is 100% correct - draw a diagram

Perhaps you should write down the equations of motion that you know - and see how they apply to your question. (...)

 

There will be something missing. That's the reason he has to draw a diagram first. He may understand why there is only one solution to the problem, and how to put that into equation.

Edited February 10, 201114 yr by michel123456