Energy accounting in open, closed and isolated systems
Grade 11 Science Worksheet - Challenge Me
Circle the best answer, or write your answer on the line.
A motor does 300 J of work on a cart-and-ramp system. The cart gains 147 J of gravitational and 60 J of kinetic energy. How much thermal energy is made, Bo?
A motor does 800 J of work on a cart-and-ramp system. The cart gains 392 J of gravitational and 250 J of kinetic energy. How much thermal energy is made, Esme?
An electric kettle with no lid takes in 300 kJ. The water gains 250 kJ of thermal energy and 30 kJ leaves with the steam. Where are the other 20 kJ, Jun?
- Warming the kettle and the room air
- Stored as gravitational energy in the steam
- Destroyed in the heater
Why is a kettle with no lid an open system, Kira?
- No energy can cross its boundary
- Steam, which is matter, leaves it
- Its water stays inside the kettle
What change would make a lidless kettle a closed system, Luz?
- Thick insulation, with the top still open
- A tight lid, so no steam escapes
- A bigger heater
Milo says friction destroys energy when a box slides to a stop. Agree or disagree?
- Disagree: it becomes thermal energy
- Agree: the kinetic energy is gone for good
- Agree: the box ends with less energy, so energy was lost from the world
Noah says the total energy of an isolated system stays the same, even with friction inside it. Agree or disagree?
- Agree: friction moves energy between stores
- Disagree: isolated systems leak heat
- Disagree: friction uses energy up
Pia says a closed system's total energy can change. Agree or disagree?
- Agree: energy can cross its boundary
- Disagree: its matter stays the same, so its energy does too
- Disagree: closed means nothing crosses
A drone's battery gives out 900 J while it lifts a 2 kg box 30 m at a steady speed. With g = 9.8 m/s², how much goes to heat and moving air, Ren?
- 1488 J
- 312 J
- 588 J
A spring launcher stores 12 J. The ball it launches leaves with 9 J of kinetic energy. Where did the other 3 J go, Tala?
- Back into the spring
- Into the ball's mass
- Thermal energy and sound in the launcher