First step: Power = (work done) / (time to do the work).
3490 watts = (work done) / (3 seconds)
3490 joules/second = (work done) / (3 seconds)
Multiply each side by 3 seconds:
Work done = (3490 x 3) joules = 10,470 joules
Second step: Weight = (mass) x (gravity)
Weight of the crate = (425 kg) x (9.8 m/s²)
= 4165 newtons
Step 3: Work done = (force) x (distance)
= (weight) x (distance lifted)
10,470 joules = (4165 newtons) x (distance)
Divide each side by 4165 newtons:
Distance = 10,470 kg-m²/sec² / 4165 kg-m/s²
= 2.514... meters (rounded)
You asked: "How can you calculate ... ?" Notice that I did the same thing in all 3 steps ... write down the formula for finding a quantity, then write the numbers you know into the formula to find the quantity.
THAT's "how", and it all boils down to knowing the formulas and picking the right one to work with. The right one to pick is the one that talks about all (or most) of the quantities that you know AND the quantity that you're trying to find.
For example, if you need to find how long it will take your turtle to walk across the room, then you need a formula that talks about time, speed, and distance. You would not get much help from the formula that talks about the pressure and volume of a gas, or one that talks about the frequency and wavelength of light waves, or Einstein's formula E=mc² for the equivalency of mass and energy.
