Define a design problem and weigh trade-offs

Answer Key - Grade 11 Science Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.

1. 1.

   A hallway lamp must run 6,000 h. Each 60 W bulb lasts 1,000 h and costs $1. Power costs 12¢ per kWh. What is the total cost of bulbs and power, Ari?

   $49.20
2. 2.

   A stairwell lamp must run 50,000 h. Each 10 W bulb lasts 25,000 h and costs $4. Power costs 12¢ per kWh. What is the total cost of bulbs and power, Esme?

   $68

3. Read this first

   Use this

   Desk-lamp bulbs, each about 800 lumens (power and life follow DOE's comparisons; prices are example data) (example data). Columns: bulb, power (W), life (h), price ($), contains mercury?. A, incandescent, 60, 1000, 1, no; B, CFL, 15, 10000, 3, yes; C, LED, 10, 25000, 4, no; D, premium LED, 8, 25000, 7, no. Constraints: at most 20 W, at most $5, and no mercury.

4. 3.

   The school adds a third limit: no mercury in classrooms. Which one bulb passes all three limits, Kira?

   • B, the CFL, which uses 15 W
   • C, the LED
   • D, the premium LED, which uses the least power
   • A, the incandescent, which costs the least

5. Use this

   Desk-lamp bulbs, each about 800 lumens (power and life follow DOE's comparisons; prices are example data) (example data). Columns: bulb, power (W), life (h), price ($), contains mercury?. A, incandescent, 60, 1000, 1, no; B, CFL, 15, 10000, 3, yes; C, LED, 10, 25000, 4, no; D, premium LED, 8, 25000, 7, no. Constraints: at most 20 W and at most $5.

6. 4.

   Bulb D costs $3 more than bulb C and lasts as long. What does the table say the extra $3 buys, Luz?

   • No mercury, which C contains
   • Light of 800 lumens, which C does not give
   • Twice the life of C, so half the replacements
   • 2 W less power, a small gain
7. 5.

   A spec says: 'The lamp must cost at most $20 and use as little power as possible.' Which part is a criterion, Milo?

   • Use as little power as possible
   • Both parts are criteria, since both involve money
   • Neither part, since power cannot be measured
   • Cost at most $20
8. 6.

   A spec lists 'at least 300 lux at the desk', 'light as even as possible' and 'under 15 W'. Which two are constraints, Noah?

   • At least 300 lux, and light as even as possible
   • Light as even as possible, and under 15 W
   • Not one, since a spec lists goals and not limits
   • At least 300 lux, and under 15 W
9. 7.

   A team says 'cheaper is better' for bulb price, but the school also caps price at $5. How is price written in the spec, Pia?

   • As neither, since price is not a design feature
   • $5 as a constraint, and cheaper as a criterion
   • $5 as a criterion, since cheaper is better
   • As a constraint, since $5 is a number
10. 8.

    A lamp is split into light source, stand and cord. Ren tests each part alone and all three pass. What comes next?

    • Test the assembled lamp, since the parts may affect each other
    • Nothing more, since the three parts passed their own tests
    • Retest the cord, since it is the weakest part of the lamp
    • Retest the light source, since it is the hottest part
11. 9.

    A hot bulb sits close to a plastic stand. The bulb and the stand each passed alone. What does that show, Tala?

    • Neither test checked how the bulb's heat affects the stand
    • The bulb must be changed to a cooler type of bulb
    • The lamp is safe, since both parts passed their own tests
    • The stand must be made of metal instead of plastic
12. 10.

    Which split of the lamp problem gives parts that can be solved and tested separately, Zee?

    • The bulb, the bulb's color and the bulb's price, as three parts
    • Cheap parts, good parts and safe parts, each tested in turn
    • The first half of the lamp and the second half, split down the middle
    • Light source, stand and power supply, each with its own target