# Physics Problem

• Jun 6th 2010, 04:37 PM
Honorable24
Physics Problem
A truck falls off a cliff. If the cliff is 33.5 m high, how much time for the truck to reach the bottom?

Displacement = -33.5m
Acceleration = 9.8 m/s^2
t = ?
I can't use any of my equations because I need at least 2 known variables
• Jun 6th 2010, 04:41 PM
TheEmptySet
Quote:

Originally Posted by Honorable24
A truck falls off a cliff. If the cliff is 33.5 m high, how much time for the truck to reach the bottom?

Displacement = -33.5m
Acceleration = 9.8 m/s^2
t = ?
I can't use any of my equations because I need at least 2 known variables

Remember at the instant when the truck falls off the cliff its inital velocity in the y direction is \$\displaystyle v_{y}=0\$.

Now you know both the intial velocity and the acceleration.
• Jun 6th 2010, 04:45 PM
Honorable24
should I make the acceleration a negative number because I keep getting a negative number that doesn't make sense?
• Jun 6th 2010, 04:52 PM
TheEmptySet
Quote:

Originally Posted by Honorable24
should I make the acceleration a negative number because I keep getting a negative number that doesn't make sense?

Just make sure to draw a sketch and make sure that your coordinate system is oriented correctly. Remember the signs come from how you set up the coordinates.