Introduction to SAT II Physics

however. That means that the potential energy of the object before it is released is equal to the
kinetic energy of the object when it hits the ground.
When the object is dropped, it has a gravitational potential energy of:

By the time it hits the ground, all this potential energy will have been converted to kinetic energy.
Now we just need to solve for v:

EXAMPLE 2

Consider the above diagram of the trajectory of a thrown tomato:

1. .At what point is the potential energy greatest?


2. .At what point is the kinetic energy the least?


3. .At what point is the kinetic energy greatest?


4. .At what point is the kinetic energy decreasing and the potential energy increasing?


5. .At what point are the kinetic energy and the potential energy equal to the values at position A?

The answer to question 1 is point B. At the top of the tomato’s trajectory, the tomato is the greatest
distance above the ground and hence has the greatest potential energy.
The answer to question 2 is point B. At the top of the tomato’s trajectory, the tomato has the
smallest velocity, since the y-component of the velocity is zero, and hence the least kinetic energy.
Additionally, since mechanical energy is conserved in projectile motion, we know that the point
where the potential energy is the greatest corresponds to the point where the kinetic energy is