An electric motor and a single-fixed pulley work together to lift a 1,000 kg crate 50.0 m. how much work was done?

a) 50,000 j
b) 20 j
c) 500,000 j
d) 1,000 j

  C)  500,000 J

The change in potential energy is ...

  Mgh = (1000 kg)(9.8 m/s^2)(50 m) = 490,000 J . . . . roughly matches C

Comments on the problem

The efficiency of the motor is unknown, so the amount of energy spent as heat is unknown.

In the equation above, we have used M for mass, and m for meters. The acceleration due to gravity is approximately 9.8 m/s^2, varying depending on location and height above the Earth. The "standard" value for g will add a few more joules to this value, but will not make it 500,000.

a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation:

d. platinum would have the greatest temperature increase because it has the lowest specific heat.