Energy accounting in open, closed and isolated systems
Grade 11 Science Worksheet - Building Confidence
Circle the best answer, or write your answer on the line.
A motor does 250 J of work on a cart-and-track system, while 90 J of heat leaves it into the room. By how much does the system's energy grow, Ari?
A motor does 500 J of work on a cart-and-track system, while 320 J of heat leaves it into the room. By how much does the system's energy grow, Bo?
A motor does 1200 J of work on a cart-and-track system, while 750 J of heat leaves it into the room. By how much does the system's energy grow, Esme?
Read this first
Use this
Energy bar chart (example data), one bar per energy store, height in J. Before: kinetic 0 J; thermal 0 J. After: kinetic 150 J; thermal 50 J. A transfer arrow goes from the motor to the cart and track, labeled work 200 J. A dashed system boundary surrounds the cart and the track. The motor is outside it; its work arrow crosses the boundary inward.
In the energy bar chart, how much energy crosses the system boundary, Jun?
- 50 J
- 150 J
- 200 J
In the energy bar chart, how much of the motor's work ends up as thermal energy, Kira?
- 150 J
- 50 J
- 200 J, the whole amount
In the energy bar chart, why do the system's stores grow, Luz?
- The track adds extra energy to the cart
- Energy is made inside the system
- Work from the motor crosses into the system
A pot of soup simmers on a stove with no lid. Steam escapes and heat flows in. What kind of system is the soup, Milo?
- Isolated: nothing crosses
- Closed: energy crosses but matter does not
- Open: matter and energy cross
Two carts collide inside a sealed box. Treating the box as perfectly insulated, what kind of system is it, Pia?
- Closed: energy crosses but matter does not
- Open: matter and energy cross
- Isolated: nothing crosses
A box slides to a stop on a rough floor. Where did its kinetic energy go, Ren?
- Into gravitational energy
- It was destroyed
- Into thermal energy in the box and floor
A cart's brake pads squeal and warm as it slows. Which stores gain energy, Zee?
- Gravitational energy, since it slows
- Thermal energy and sound
- Kinetic energy