hi

the answer is D)

i did v=10/25=0,4m/s

P=Fv=20 * 10 * 0,4 = 80W

What did i do wrong?

Hey, this is how i did it;

when the mass is being elevated it gains gravitational potential energy.

P.E=mgh

20 * 10 * 10=2000J

Power=work/time ,

work is the energy transferred

when h=10m ,t=20

so, P= 2000/20 =100W

I dont know if this is the correct way. If it isn’t, please let me know .

Isn’t the time is 25 when the height is 10m?

Juliette, there is nothing wrong with your calculation i guess

hey, I’m really sorry i put the wrong answer here. I checked it again and this is what i found, look at the constant region of the graph. since a change in height of 10m (5-15) takes a time of 20 seconds (15-35), that’s the reason i took the time as 20 sec for a height of 10m.

Ohh i see u took the the constant slope instead of the literal 10m. I think that’s also a good idea.

I guess we can also make approximation about the final answer like Juliette got 80 W which is quite close to 100W in the given, right?

Hey, I think so that you can use the same method. Please confirm it anyway.