TPR Diagnostic 5 - PS #23

[pm1]

So here is the question: (simple but I am a bit confused... )

An ideal machine consumes 20 kJ of energy to lift an object to a height of 50 cm. Which one of the following best approximates the mass of the object?
A) 4 × 10^–1 kg
B) 4 × 10^1 kg
C) 4 × 10^3 kg
D) 4 × 10^4 kg

Answer: C

I now get it that E=mgh. But why can't we use the equation W = F x d. Shouldn't it give the same answer? Is energy and work interchangeable? Thank you!

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[MedPR]

So here is the question: (simple but I am a bit confused... )

An ideal machine consumes 20 kJ of energy to lift an object to a height of 50 cm. Which one of the following best approximates the mass of the object?
A) 4 × 10^–1 kg
B) 4 × 10^1 kg
C) 4 × 10^3 kg
D) 4 × 10^4 kg

Answer: C

I now get it that E=mgh. But why can't we use the equation W = F x d. Shouldn't it give the same answer? Is energy and work interchangeable? Thank you!

Yes, W=Fd works as well.

20*10^3 = m*10*0.5

m=4*10^3 kg

 

[pm1]

Yes, W=Fd works as well.

20*10^3 = m*10*0.5

m=4*10^3 kg

wow.. nvm, I was having trouble with my math!

thank you though!

 

[Class1P]

always remember your units