- #1
Qube
Gold Member
- 468
- 1
Homework Statement
A car starts from rest. With constant acceleration, the car increases its speed from 10m/s to 50m/s over a distance of 60m. How long does this take?
Purported answer: 4.0s
Homework Equations
Constant acceleration, so the following equations apply:
Vf^2 = Vi^2 + 2ad
Vf = Vi + at
The Attempt at a Solution
Vf^2 = Vi^2 + 2ad
2500 = 100 + 2a(60)
2400 = 120a
240/12 = a
a = 20 m/s^2.
Vf = Vi + at
50 = 10 + 20(t)
40/20 = 2s.
Why does the key say 4s?
I'm guessing it's because the key is wrong!