Physics
posted by Unknown .
a motor lifts a 12 kg mass to a height of 15 meters at a content velocity in 3.5 seconds.
a) find the power
b) if the motor is only 35% efficient find the input energy

change in potential energy = m g h = 12 * 9.81 * 15 = 1766 Joules
power = joules per second = 1766/3.5 =505 Watts
Input power = 505/.15 = 3363 Watts
Input energy = 3363 Watts * 15 seconds = 50,451 Joules
Respond to this Question
Similar Questions

Physics
A 120V motor has mechanical power output of 2.00 hp. It is 82.0% efficient in converting power that it takes in by electrical transmission into mechanical power. (a) Find the current in the motor (b) Find the energy delivered to the … 
physics
A 120V motor has mechanical power output of 3.20 hp. It is 81.0% efficient in converting power that it takes in by electrical transmission into mechanical power. (a) Find the current in the motor. Answer: 24.6A (b) Find the energy … 
Physics :)
A motor lifts a 70.0 kg box off the ground, starting from rest. In 8.00 seconds it lifts the box to a height of 20.0 m. At that time, the box is moving upward with a velocity of 5.00 m/s. What is the average power of the motor during … 
Physics
An electric motor develops 70 kw of power as it lifts a loaded elevator 28.5 m in 42 seconds. How much force does the motor exert? 
physics
A 120V motor has mechanical power output of 2.20 hp. It is 92.0% efficient in converting power that it takes in by electrical transmission into mechanical power. (a) Find the current in the motor (A) (b) Find the energy delivered … 
PHYSICS.
5. A motor lifts a 12 kg mass to a height of 15 m at a constant velocity in 3.5 s. a) Find the power b) If the motor is only 35% efficient find the input energy. 
Physics
A lift of mass 200kg moves upward with a uniform velocity of 4 m/s . if efficiency of motor is 70% then input power of motor is? 
Physics
An electric motor runs at a constant rotational frequency of 3000 r/min and has the load of 75 Nm and a 5,0 Nm extra load of friction and gear. The efficiency of the motor is 78%. a) What is the input power of the motor? 
Physics
Searches related to a motor lifts an elevator of mass m at constant speed. The power output of the motor is P and there are no frictional losses so that all the power output from the motor goes into lifting the elevator mass. What … 
Physics
A motor lifts an elevator of mass m at constant speed. The power output of the motor is P and there are no frictional losses so that all the power output from the motor goes into lifting the elevator mass. What is the correct expression …