Question

which phrase is an example of kinetic energy?
a tank containing gasoline
a girl running in a race
a car sitting motionless
a sled sitting at the top of a hill
question 5
1 pts
which type of energy does a ball falling through the air have?
only kinetic energy because it still has a distance to move before it hits the ground
only potential energy because it is moving
potential energy because it still has a distance to move before it hits the ground and kinetic energy because it is moving
kinetic energy because it still has a distance to move before it hits the ground and potential energy because it is moving

Explanation:

• Kinetic energy is the energy of motion. A girl running in a race is in motion, so she has kinetic energy. A tank containing gasoline has chemical potential energy. A car sitting motionless has no kinetic energy (it has potential energy if on a hill etc., but not kinetic). A sled sitting at the top of a hill has potential energy (due to its height).
• For the ball falling through the air: Potential energy is related to height (\(U = mgh\), where \(h\) is the height above the ground). Kinetic energy is related to motion (\(K=\frac{1}{2}mv^{2}\)). Since the ball is moving (has a non - zero \(v\)), it has kinetic energy, and since it has a height \(h>0\) above the ground (before hitting the ground), it has potential energy.

Answer:

• First question: B. a girl running in a race
• Second question: C. potential energy because it still has a distance to move before it hits the ground and kinetic energy because it is moving