• Support PF! Buy your school textbooks, materials and every day products Here!

Motor power in Kw

  • Engineering
  • Thread starter enginecadet88
  • Start date
  • #1

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, im 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?


Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
mgb_phys
Science Advisor
Homework Helper
7,774
12
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.
 
  • #3
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.
 
  • #4
mgb_phys
Science Advisor
Homework Helper
7,774
12
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)
 

Related Threads for: Motor power in Kw

Replies
1
Views
640
  • Last Post
Replies
1
Views
641
Replies
3
Views
822
Replies
1
Views
9K
Replies
6
Views
2K
Replies
0
Views
1K
  • Last Post
Replies
4
Views
6K
Replies
15
Views
682
Top