Educational worksheet on work, power, and energy calculations featuring real-world scenarios like climbing stairs, using a forklift, and operating a crane.

Let’s solve each problem step by step. We’ll use the formulas given:

Work against gravity:
> W = m · g · h
Where:
- m = mass in kg
- g = 9.81 m/s² (gravity)
- h = height in meters
→ Work is measured in Joules (J)

Power:
> P = W / t
Where:
- W = work in Joules
- t = time in seconds
→ Power is measured in Watts (W)

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Problem 1:

Sabrina walks up stairs.
Mass (m) = 50 kg
Height (h) = 3.4 m
g = 9.81 m/s²

Work = m · g · h
= 50 × 9.81 × 3.4
First, 50 × 9.81 = 490.5
Then, 490.5 × 3.4 = let’s calculate:
490.5 × 3 = 1471.5
490.5 × 0.4 = 196.2
Total = 1471.5 + 196.2 = 1667.7 J

✔ Answer for #1: 1667.7 Joules

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Problem 2:

Time (t) = 20 seconds
Use work from #1: W = 1667.7 J

Power = W / t = 1667.7 / 20 = 83.385 Watts

✔ Answer for #2: 83.385 Watts

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Problem 3:

Forklift lifts crate.
Mass (m) = 250 kg
Height (h) = 2.2 m
g = 9.81 m/s²

Work = m · g · h
= 250 × 9.81 × 2.2
First, 250 × 9.81 = 2452.5
Then, 2452.5 × 2.2 =
2452.5 × 2 = 4905
2452.5 × 0.2 = 490.5
Total = 4905 + 490.5 = 5395.5 J

✔ Answer for #3: 5395.5 Joules

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Problem 4:

Time (t) = 1.6 seconds
Use work from #3: W = 5395.5 J

Power = W / t = 5395.5 / 1.6
Let’s divide:
5395.5 ÷ 1.6
Multiply numerator and denominator by 10 to make it easier:
53955 ÷ 16 = ?

16 × 3372 = 53952 → remainder 3
So 3372 + 3/16 = 3372.1875

Wait — that can’t be right because 5395.5 ÷ 1.6 should be around 3372? Let me recalculate:

Actually:
5395.5 ÷ 1.6
= (5395.5 × 10) ÷ 16 = 53955 ÷ 16

Do division:
16 × 3372 = 53952 → so 53955 - 53952 = 3 → 3372 + 3/16 = 3372.1875

But wait — that seems too high. Did I mess up?

Wait — no, actually, 5395.5 ÷ 1.6:

Try this way:
1.6 × 3000 = 4800
Subtract: 5395.5 - 4800 = 595.5
1.6 × 372 = 595.2
So total = 3000 + 372 = 3372, with 0.3 left → 0.3 / 1.6 = 0.1875
So yes, 3372.1875 Watts

That’s correct — lifting 250 kg quickly takes a lot of power!

✔ Answer for #4: 3372.1875 Watts

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Problem 5:

Crane lifts steel beams.
Mass (m) = 4000 kg
Height (h) = 45 m
g = 9.81 m/s²

Work = m · g · h
= 4000 × 9.81 × 45
First, 4000 × 9.81 = 39240
Then, 39240 × 45
Break it down:
39240 × 40 = 1,569,600
39240 × 5 = 196,200
Total = 1,569,600 + 196,200 = 1,765,800 J

✔ Answer for #5: 1,765,800 Joules

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Problem 6:

Time = 4 minutes → convert to seconds:
4 × 60 = 240 seconds
Use work from #5: W = 1,765,800 J

Power = W / t = 1,765,800 / 240
Divide:
1,765,800 ÷ 240
Simplify: divide numerator and denominator by 10 → 176,580 ÷ 24
Now divide 176,580 ÷ 24:

24 × 7000 = 168,000
Subtract: 176,580 - 168,000 = 8,580
24 × 357 = 8,568 (since 24×350=8400, 24×7=168 → 8400+168=8568)
Remainder: 8,580 - 8,568 = 12 → 12/24 = 0.5
So total = 7000 + 357 + 0.5 = 7357.5 Watts

✔ Answer for #6: 7357.5 Watts

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Final Answer:
1. 1667.7 J
2. 83.385 W
3. 5395.5 J
4. 3372.1875 W
5. 1,765,800 J
6. 7357.5 W