# I need help in these problems please

How do you do these problems:

1) What is the magnitude of the force required to accelerate an electron of mass 9.1x10^-31 kg from rest to a speed of 2.0x10^7 m/s for a distance of 0.5 cm

(a) 1.8 x 10^-21 N
(b) 9.0 x 10^-19 N
(c) 1.8 x 10^-16 N
(d) 3.6 x 10^-14 N

2) In an elevator system, a motor rotates a shaft wrapping or unwrapping a chain that raises or lowers the elevator car. The car's mass is 1.20x10^3 kg and is designed to carry a maximum load of 9.5x10^2 kg. While in motion, a constant frictional force of 3.5x10^4 N acts on the car.

(a) What power must the motor deliver to raise the fully loaded car at a speed of 2.5 m/s?

(b) The elevator system is modified by connecting a free-hanging 5.0x10^2 kg counterweight to the chain that passes over the shaft of the motor, as shown below. What power must the motor now deliver to raise the fully loaded car at a speed of 2.5 m/s?

Thank you very much

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cristo
Staff Emeritus

Do you have any thoughts on the questions?

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for #1 I used W = Fd. I changed the .5cm to .005m but i quite cannot get the answer.

I have no clue about #3 :(

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cristo
Staff Emeritus
for #1 I used W = Fd. I changed the .5cm to .005m but i quite cannot get the answer.
This isn't showing your working; it is a stating one brief point. How do you intend to use work to solve this problem?
I have no clue about #3 :(
Well, to start with, do you know any equations relating power and force?

yeah I know P = W/T

for #2, I have this answer written down which is C but I don't know how I got it because I just punched numbers into the calculator omg I'm so screwed

can somebody really help me? I have been trying since yesterday. Please