Question

What would we need to know to calculate both work and power? (2 points) Select one: a. energy, force, and time b. force, distance, and time c. force, mass, and distance d. mass, force, and energy

Answer 1

Answer:

B. force, distance, and time

Explanation:

I did the test and got it.

Answer 2

B. force, distance, and time

Take a look at the definition of a Joule (SI unit of work) and the definition of a Watt (SI unit of power). They're (kg*m^2)/s^2 for work and (kg*m^2)/s^3 for power. Another definition for work is Newton Meter which is force times distance, and since you can define work as force times distance, then power is work per second. So it looks like you need force and distance to calculate work, and then time since power is work over time. So of the 4 choices, we've been given, let's see if any of them allow us to calculate both work and power.

a. energy, force, and time
* OK. Force will get us Newtons. But how much work do you have, don't know. Since work is force times distance. So can't get work. And without getting work, can't get power. Wrong answer.

b. force, distance, and time
* Force over distance nicely defines work. And time is essential since power is work over time. So this looks to be very good choice.

c. force, mass, and distance
* Have a problem here. Time is pretty essential since all of the SI units for work and power have seconds hiding somewhere in their definition. So this is the wrong answer.

d. mass, force, and energy
* Same issue, no time element here. So wrong answer.