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Sports Physics 6-8 / Week 07 / Game Day
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Week 07 · Potential Energy: Height and Stretch

Game Day

Game Day: Ramp contest
// Energy that waits
⏱ about 20 min

Game Day: Ramp Contest

Saturday morning, the cardboard ramp waits on the patio beside a tall stack of books and one soft ball.

"Pick your height," Rocket says. "One book to five. Predict your roll distance, then roll."

Raven writes a column for guesses and a column for real numbers. "Closest guess wins, not the longest roll."

Nova hovers above the stack. "What makes a guess good?" she asks.

"Using yesterday's data," Rocket says. "More books, more stored energy, longer roll. But not forever."

The first roll from four books streaks across the patio and onto the grass, where it stops fast.

"What do you notice?" Raven asks. "The grass ate the energy."

Nova's light glows. "Friction again. Keep that thought for next week."

  1. Potential energy is energy stored because of position, shape or arrangement, and it can be recovered.
  2. Lifting a ball stores gravitational potential energy. Higher means more stored.
  3. Stretching, squeezing or bending something springy stores elastic potential energy.
  4. Released stored energy becomes kinetic energy. A ball from a higher ramp reaches the bottom faster.
  5. The same lift stores more energy where gravity is stronger, so the amount depends on the arrangement of the two objects.
◇ FAMILY RAMP CONTEST
Set the cardboard ramp on one book on a smooth floor or patio. Tape a start line at the bottom.
Each person picks a number of books, one to five, and writes a guess for how far the ball will roll.
Roll the ball from that height, letting it go without a push. Measure from the start line to where it stops.
Score by how close each guess was. Then try two heights nobody picked and guess again.
Talk it over. Did the roll grow by the same amount for each added book? What stopped the ball every time?
For a grown-up
The ramp leans on books on the floor or a low step, never on a table edge or a railing.
Soft ball only, rolled along the ground. Choose a lane away from roads, stairs and younger children.
The potential energy ideas this week come from an OpenStax physics text at openstax.org and the NASA planetary fact sheet at nasa.gov.
Safety first
Nothing is thrown, and no one climbs to make a taller ramp.
Keep the lane clear while the ball is rolling.
Wear shoes outdoors and drink water on a hot day.
THINK IT THROUGH
  • Read the question.
  • Tap your answer.
Someone picks five books and someone picks one. Whose ball has more stored energy at the top?
The ball rolled onto grass and stopped fast. Where did its kinetic energy go?
Game Day checkTrue or false?
A ball on a higher ramp stores more potential energy.?
Pushing the ball at the start would be a fair test of the ramp height.?
Stored energy becomes kinetic energy as the ball rolls down.?
WHY THIS EXERCISEThe contest is the whole week in one roll: store it, release it, watch it move.
Draw the ramp at the height you picked, the ball at the top and the spot where it stopped. Label stored and moving.
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