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A motor having a maximum power rating of 8.1 x 104 watts is used to operate an elevator with a weight of 1.8 x 104 newtons. What is the maximum weight this motor can lift at an average speed of 3.0 meters per second?

Respuesta :

If the power rating of the motor is 8x10^4 Watts and our equation for Power is:

[tex]Power=\frac{Energy}{time}=\frac{Work}{time}=\frac{Force \times Displacement}{time}\\\\P=Force \times Velocity[/tex]

Note that:

[tex]F=ma=mg[/tex]

where g is the average gravity on Earth which is approximately 9.8 m/s^2.

And so:

[tex]P=F \times V\\P=m \times g \times V\\\\\ m=\frac{P}{gv} \\\\[/tex]

[tex]m=\frac{8.1 \times 10^4 }{9.8 \times 3} =2755.1kg[/tex]

In terms of force:

[tex]F=mg=2755.1kg \times 9.8 \frac{m}{s^2}=27000N[/tex]


The maximum weight of motor that can lifted at the given speed is of 27000 N.

Given data:

The maximum power rating of the motor is, [tex]P = 8.1 \times 10^{4} \;\rm W[/tex].

The weight of elevator is, [tex]W = 1.8 \times 10^{4} \;\rm N[/tex].

The speed of motor is, v = 3.0 m/s.

Since, the power rating of motor is obtained due to the force experienced on the elevator. Then,

[tex]P = F \times v[/tex]

Solving as,

[tex]8.1 \times 10^{4} = F \times 3.0 \\F = 27000 \;\rm N[/tex]

Now, the force experienced on the elevator is due to the weight of motor. Then,

Force (F) = Weight of motor (W')

[tex]27000 = W' \\\\W' = 27000 \;\rm N[/tex]

Thus, we can conclude that the maximum weight of motor that can lifted at the given speed is of 27000 N.

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