Question

get the gizmo ready:

• select two sleds.
• check that show energy is on.
• set the red sled mass to 150 kg and its height to 20 m. set the blue sled mass to 100 kg and its height to 35 m.

activity c: sled wars!
introduction: burt the yeti and his friend karen are having a contest called a “sled war.” the winner is the sled that pushes the other sled backward when the two sleds collide.
question: who will win the sled war?

1. predict: burt’s red sled is a bit heavier than karen’s blue sled, but she is higher on the slope.

a. what is the potential energy of each sled?
red sled: ______
blue sled: ______
b. which sled do you think will push the other back when they collide? ______
explain. ______

Explanation:

Step1: Calculate red sled PE

Gravitational potential energy is $PE = mgh$, use $g=9.8 \frac{m}{s^2}$.
$PE_{\text{red}} = 150 \times 9.8 \times 20 = 29400 \ J$

Step2: Calculate blue sled PE

$PE_{\text{blue}} = 100 \times 9.8 \times 35 = 34300 \ J$

Step3: Compare energies to find winner

The sled with greater potential energy will push the other back when colliding.

Answer:

A. Red sled: $29400 \ J$, Blue sled: $34300 \ J$
B. The blue sled will push the red sled back.