Difficulties with physicsWatch
Hi I have difficulty for solving physics problems. i always need a lot of time to solve problems. Could you help me? Do you know what is the best way to improve my physics problem?
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1. Write all of the data that we know, including data calculated from the questions before, even if it is in the question.
2. Select all the formulae you know that have the value in that we're working out.
3. Rearrange as necessary.
4. Substitute and simplify.
5. Give to the required amount of precision as indicated by the question or from other values (when dealing with significant figures, always give the answer to the degree of the least significant value).
A bar has a constant current of 8000 A. The resistance in a 1.0 m length of the bar is 2.7 ✕ 10^-6. Calculate the power dissipated as heat along a 1.0 m length of it.
The information we know is:
- current = 8000 A
- resistance = 2.7 ✕ 10^-6
- length = 1.0 m
- power = ? W
And take a look at a formulae booklet (or recall some formulae that you know) that contain the above information and that can be used to calculate the power:
1. P = VI
2. P = (I^2)R
3. P = (V^2)/R
We already know the current and resistance in the wire, and we know that we must consider the resistance because it is the power dissipated as heat (from physics theory). Therefore, we must use equation 2. The equation is already solved for P, power, so we can just stick it in a calculator.
P = (I^2)R
P = 8000^2 ✕ (2.7✕10^-6) = 170 W (to 2 significant figures).