Here is the question, it is very simple.(adsbygoogle = window.adsbygoogle || []).push({});

A toy car accelerates by means of a rocket-type engine for 20 m. If the acceleration during the burn is [tex]5 m/s^2[/tex] and the burn lasts for 3 s, determine the velocity of the car at the end of the burn.

It seems like the obvious one, and we use.

[tex]v=v_i + at[/tex]

...and we get 15. This works for uniform acceleration, which it says it is.

They are using...

[tex]s = v_f t - 1/2 a t^2[/tex]

They got that by differentiating from [tex]v_i[/tex], instead of the usual [tex]v_f[/tex]

In the end, they get 14.2 m/s.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# This has to be wrong

**Physics Forums | Science Articles, Homework Help, Discussion**