A motorboat travelling on a straight course slows uniformly from 60km/h to 40km/h in a distance of 50m?

A motorboat travelling on a straight course slows uniformly from 60km/h to 40km/h in a distance of 50m, What is the boats acceleration?

Here is what I have:
vo=60km/h
v=40km/h
d=50m
I used the formula
v^2=vo^2+2ad
Which I got a=-0.056m/s^2.


Can anyone confirm that? Thanks? (Sorry studying for a test and want to see if I am on the right track)

Do your own hwk little girl

Working initially in km and hr:
40^2 = 60^2 + 2a * 50 * 10^(- 3)
a = (40^2 - 60^2) / (2 * 50 * 10^(- 3))
= - 20000 km / hr^2
= - 20000 * 10^3 / 3600^2
= - 1.54 m/s^2.

Converting to m and sec. initially:
40 km / h = 40 * 10^3 / 3600 = 11.111 m/s.
60 km / h = 60 * 10^3 / 3600 = 16.667 m/s.
a = (11.111^2 - 16.667^2) / (2 * 50)
= - 1.54 m/s^2.

You appear to have left out one of the 3600 conversion factors. The acceleration conversion is from km / hr^2 to m / sec^2. Apart from that, you're on track OK.