Grade 8 Physics practice

What is on the worksheet

1. A model device transfers energy at constant power 675 W for 66 s. Find the transferred energy. Round to 3 decimal places if needed. Answer in J.

2. A device receives 400 J and has useful-energy efficiency 55%. Find the useful output energy. Round to 3 decimal places if needed. Answer in J.

3. A normal force of 335 N acts uniformly over 0.4 m². Find the pressure. Round to 3 decimal places if needed. Answer in Pa.

4. A device receives 1220 J and has useful-energy efficiency 5%. Find the useful output energy. Round to 3 decimal places if needed. Answer in J.

5. An ohmic resistor of 8 Ω has potential difference 36 V. Find current. This is a paper calculation, not a construction instruction. Round to 3 decimal places if needed. Answer in A.

6. A 8 kg cart has horizontal forces 69 N right and 105 N left. No other horizontal forces act. Taking right as positive, find its acceleration. Round to 3 decimal places if needed. Answer in m/s².

7. A rover travels 148 m in 25 s, then 361 m in 51 s. Find its average speed for both stages. Round to 3 decimal places if needed. Answer in m/s.

8. Why can a hollow metal boat float when a compact piece of the same metal sinks?

9. An ohmic resistor of 14 Ω has potential difference 8 V. Find current. This is a paper calculation, not a construction instruction. Round to 3 decimal places if needed. Answer in A.

10. A model device transfers energy at constant power 635 W for 27 s. Find the transferred energy. Round to 3 decimal places if needed. Answer in J.

11. A model device uses constant power 250 W for 7 h. Find the energy in kilowatt-hours. Round to 3 decimal places if needed. Answer in kWh.

12. A device receives 510 J and has useful-energy efficiency 30%. Find the useful output energy. Round to 3 decimal places if needed. Answer in J.

13. On a weightless balanced beam, 109 N acts 1 m left of the pivot. What downward force at 6 m right balances it? Forces are perpendicular to the beam. Round to 3 decimal places if needed. Answer in N.

14. A constant current of 1.4 A flows for 135 s. Find transferred charge. Round to 3 decimal places if needed. Answer in C.

15. A device receives 1490 J and has useful-energy efficiency 55%. Find the useful output energy. Round to 3 decimal places if needed. Answer in J.

16. An ohmic resistor of 13 Ω has potential difference 28 V. Find current. This is a paper calculation, not a construction instruction. Round to 3 decimal places if needed. Answer in A.

17. A 3 kg load is raised vertically by 19 m in a field g = 10 N/kg. Find its gravitational potential-energy gain. Round to 3 decimal places if needed. Answer in J.

18. A 14 kg cart has horizontal forces 24 N right and 112 N left. No other horizontal forces act. Taking right as positive, find its acceleration. Round to 3 decimal places if needed. Answer in m/s².

19. A rover travels 279 m in 75 s, then 177 m in 14 s. Find its average speed for both stages. Round to 3 decimal places if needed. Answer in m/s.

20. 55 complete oscillations take 49 s. Find the period. Round to 3 decimal places if needed. Answer in s.