Efficiency/power problem?

Question

A motor having an efficiency of 88% operates a crane having an efficiency of 42%. With what constant speed does the crane lift a 410kg crate of machine parts if the power supplied to the motor is 5.5kW?

Power=Force*Velocity
so
5.5=velocity*force
how do you find force?

Answer 1

The net efficiency of the system is (.88)(.42) = 37%.

To lift the crate with constant speed requires a force equal to the weight of the crate, mg = ( 410 kg ) ( 9.8 m/s^2 ) = 4000 N (to two significant figures).

The rate at which the motor does work is ( 5500 W ) ( .37 ) = 2000 W.

Work = Force multiplied by distance. You can do 2000 J of work each second. This will move a 4000-N crate 1/2 meter per second. So the speed is .5 m/s.

Answer 2

The force is the same as the weight of the object (not the mass). But remember that the power must be reduced by the efficiencies.

Power supplied = 5.5
Power output from motor = 5.5 *.88 = power input to crane
Power output from crane = 5.5 * .88 *.42 = 2.03 kW

1 W = 1N m / s
1 kW = 10^3 N m / s

2.03 X10^3 N m / s = v m/s * 410 kg * 9.8 m * s ^-2

2.03 x 10^3 N m / s = v * 410 *9.8 (kg m / s^2) m / s
= v * 4018 N m/s = v*4.018 x 10^3 N m/s
Units check

v = 2.03 / 4.018 = .505 m/s

Answer 3

Will have to calculate the power .

The power input to 5.5KW and it is 88% efficient .
88% = 4840 W.

Now Crane has 42% effciency
42% = 2032.8 W.

Power = Force X Velocity .
2032.8 = (410*9.8)Xvelocity .

Velocity = 0.5059233449ms^-1

Force = weight
Why??
Moving at constant speed .
Force(weight) - R=ma
a=0
Force = weight .

Answer 4

ok, if there's a god, what form of tension/skill/skill ought to create and uphold any such supernatural entity? Do you get my factor? the two way you settle for that something existed first and not using a "author"...the greater logical option to me is the universe.

Answer 5

i wish i could help you but im just as clueless as you!!