The charger has a power output of 7000 W.
Calculate the time taken to transfer 420 000 J of energy to the car battery.
How to approach this question
1. Start with the equation from the previous question: E = P × t.
2. Rearrange the equation to make time (t) the subject.
3. Identify the values given: Energy (E) = 420 000 J and Power (P) = 7000 W.
4. Substitute these values into your rearranged equation.
5. Calculate the time. The unit will be seconds.
Full Answer
Equation: time = energy transferred / power
Substitution: time = 420 000 J / 7000 W
Answer: time = 60 s
We use the equation linking energy, power, and time:
Energy transferred (E) = Power (P) × time (t)
We need to find the time, so we rearrange the equation by dividing both sides by Power:
time (t) = Energy transferred (E) / Power (P)
Now, substitute the given values:
- E = 420 000 J
- P = 7000 W
t = 420 000 / 7000
t = 60 s
Common mistakes
✗ Incorrectly rearranging the equation (e.g., multiplying instead of dividing).
✗ Calculation error.
✗ Forgetting the unit (seconds).
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