(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A person standing on a bridge overlooking a highway inadvertently drops an apple over the railing just as the front end of a truck passes directly below the railing. If the vehicle is moving at 55km/h and is 12m long, how far above the truck must the railing be if the apple just misses hitting the rear end of the truck?

2. Relevant equations

The ones we have learned in class are the general dynamics formulas:

X = X0 + V0t + (1/2)a*t

V = V0 + at

V^2 = V0^2 + 2*a*X

3. The attempt at a solution

I drew myself a little diagram of what is happening to help clarify the problem. After that, I decided to use the distance finding formula since the question is asking about height.

X = X0 + V0t + (1/2)a*t

I set my initial distance (where the apple is dropped) to be 0. The velocity at that point in height is 0 (release). What is left is this:

X = (1/2)a*t

This is where I am getting confused, since there is acceleration of the apple (9.8m/s^2) and acceleration of the truck (horizontal). I also do not know what to use for the t (time) in the equation. Any ideas?

**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!

# Gravitational Acceleration and Determining Height

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