Thread: velocity/acceleration

A dragster races down a 400 m strip in 8 seconds. Its distance, in metres, from the starting line after t seconds is s(t)=6t^2+2t

a) find the dragster's velocity and acceleration as it cross the finish line.

b) how fast was it moving 60 m down the strip?

I need help with part b.. I thought that i would use the acceleration formula i made up in part a but it did not work out since the a(t) formula in part a is a constant number > 12

Help with part b. thanks

Originally Posted by skeske1234

A dragster races down a 400 m strip in 8 seconds. Its distance, in metres, from the starting line after t seconds is s(t)=6t^2+2t

a) find the dragster's velocity and acceleration as it cross the finish line.

b) how fast was it moving 60 m down the strip?

I need help with part b.. I thought that i would use the acceleration formula i made up in part a but it did not work out since the a(t) formula in part a is a constant number > 12

Help with part b. thanks

how did you do (a)?

For (b), set s(t) = 60 and solve for t. Then plug that t-value into the velocity equation to find its velocity at that time (why would you use acceleration??)

All you need to do is set and use the quadratic formula to solve for . Take the solution and plug it into to obtain the velocity at 60m. If you don't remember the formula to solve for , just look it up on wikipedia. Or just factor the equation. I'm bad at factoring, so I always just use the quadratic formula.