# Calculate Motor Power in kW for 15 Tonnes, 16 m, 0.2 m/s

• Engineering
In summary, the conversation revolves around choosing a motor capable of moving 15 tonnes over a distance of 16m at a speed of 0.2m/s. The equation F=ma is mentioned but it is clarified that it only calculates the force needed to accelerate the object to 0.2m/s. The equation for power in kilowatts is then discussed, with the reminder that it is mainly used to overcome friction. The concept of friction is further explained, and it is suggested to consider the type of friction involved in the specific scenario. The conversation also mentions a specific example of a crane trolley and the use of a rack and pinion set. It is stated that friction can be disregarded in this scenario,

## Homework Statement

Ok so i need to choose a motor that is capable of moving 15 tonnes (metric) over a distance of 16 m at 0.2 m/s.

So, I am guessing i need to first find the force required to move this object which would be F=m*a. Is this right?

Now, what would be the equation to find the power required in Kw?

## The Attempt at a Solution

No, f=ma is only the force needed to accelerate it upto 0.2m/s
The power is mainly to overcome friction.
You need to know what friction is involved, consider how hard it is to drag a 15tn rock over concrete compared to how much power you need to pull a 15tn boat.

Ill give some more background. The calculations i need really don't have to go into too much detail though.

This equation is for a crane trolley of 15 tonnes (metric) which moves along 2 beams. So, it is not a metal on metal contact. It will be a set of wheels or more accurately a rack and pinion set. Are there equations which do not take friction into account as i have been told by my lecturer that friction can be disregard.

Neglecting friction it takes no power to keep the trolley moving at any speed.
To get it moving you have to put in energy = 1/2 m V^2, how quickly you do this (ie how long you take to accelerte it ) determines the power (power is energy/time)

## 1. What is the formula for calculating motor power in kW for a given load?

The formula for calculating motor power in kW is P = (F x v)/1000, where P is power in kW, F is the total force in Newtons, and v is the velocity in meters per second.

## 2. How do you determine the total force for a load of 15 tonnes?

The total force for a load of 15 tonnes can be determined by multiplying the mass (15 tonnes) by the acceleration due to gravity (9.8 m/s^2). This gives a total force of 147 kN (kilonewtons).

## 3. What is the velocity used in the formula for calculating motor power?

The velocity used in the formula for calculating motor power is the linear velocity, measured in meters per second. In this case, the velocity is given as 0.2 m/s.

## 4. What is the unit of measurement used for motor power?

The unit of measurement used for motor power is kilowatts (kW), which is a unit of power equal to 1000 watts.

## 5. How do you calculate motor power for a load with a distance of 16 meters?

To calculate motor power for a load with a distance of 16 meters, you would first need to determine the time it takes for the load to travel that distance at a speed of 0.2 m/s. Then, you can use the formula P = (F x d)/t to calculate the power, where P is power in watts, F is the total force in Newtons, d is the distance in meters, and t is the time in seconds. Finally, you can convert the power to kilowatts by dividing by 1000.