# physics

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a portable electric drill produces 1.2 hp at full load. If 85% of the power provided by the 9.6 V battery pack is useful, what is the current flow? how much power goes into the waste heat?

I don't know what to do. In class, we learned about amps, volts,and resistance, but never horsepower.

the equations we used were like P=v^2/R or V=iR and stuff like that.

• physics -

The produced power is useful power, and 1.2 hp is 895 W. (1 HP = 746 watts). Therefore the electrical input power is 895/0.85 = 1053 W.

Since electrical power P = I*V, the current is P/V = 1053/9.6 = 109.7 A

The waste heat is 15% of the input power, or 158 W

• physics -

how to use formula in unit

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