What is the net force and power in a lawnmower system?

In summary, the conversation discusses the solution to a physics problem involving a person pulling a lawnmower. The problem involves finding the amount of work done by the person, the heat energy generated by friction, the rate at which the person does work, and the final speed of the lawnmower. The solution involves finding the net force in the system, which is the sum of the forces acting in the horizontal direction. After considering the direction of the handle and the force of gravity, the problem is successfully solved.
  • #1
physicsperson
20
1
[SOLVED] The NET FORCE and a lawnmower

Homework Statement


Well I am working on a question here and am finding trouble with one part. The answers are in brackets. The trouble I am having is with part c, where i believe you have to find the accleration then the time to work out power which is equal to work over time.

A person pulls on a 20 kg lawn mower with 25 N and moves it 4.5 m. The handle of the lawnmower in inclined at 15 degrees above the horizontal and the friction co-effiecient is 0.1 If vi=0 find
a.)amount of work done by person (108.7)
b.)amount of heat energy generated by friction (85.3)
c.)rate at which the person does work (18.6 Watts)
d.)the final speed of the lawnmower(1.53)



Homework Equations



p = w/t, F=ma ---> a =F/m

The Attempt at a Solution


Well part a is basicaly w= fcos15 * 4.5 m
and b is finding out friction by using force diagrams and finding Fn
but c i am not sure how to find the accel and consequently the time.

wat is the net force in the system? please help. thank you.
 
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  • #2
The net force on the system in the direction of motion is the sum of EVERY force acting on the object in that direction or the negative of that direction. In this case, your forces to be summed will be any forces acting in the horizontal direction. Can you tell me which forces fit this description?
 
  • #3
well the forces wrking in that direction are friction, the person pulling and the gravity so i would think that the net force would be Fpull - mgsin15 - Ff

but the answer i get just doesn't workout

thanks
 
  • #4
OK, by my understanding, the problem does not say that the person is pulling the lawnmower up or down a hill. How can there be a component of gravity involved if the object is not moving along a slope?
 
Last edited:
  • #5
i think we have to assume its going up
 
  • #6
I agree with G01. The lawn mower is not moving up an incline, the handle is at an angle of 15 degrees, and the force of the person pulling it is directed along that handle.
 
  • #7
physicsperson said:
i think we have to assume its going up

As hage pointed out. We do not have to assume this. Think of the man pulling at the angle of the handle, but the lawn mower still moving horizontally.
 
  • #8
Ya, you guys were right! Thank you so much! Solved!
 

1. How does the NET FORCE affect a lawnmower?

The NET FORCE is the total force acting on an object. In the case of a lawnmower, the NET FORCE is what determines its direction and speed. If the NET FORCE is greater in one direction, the lawnmower will move in that direction.

2. What factors contribute to the NET FORCE on a lawnmower?

The NET FORCE on a lawnmower is influenced by several factors, including the weight of the lawnmower, the force applied by the person pushing it, and any resistance from the grass or terrain.

3. How does the NET FORCE affect the efficiency of a lawnmower?

The NET FORCE directly impacts the efficiency of a lawnmower. If the NET FORCE is too low, the lawnmower may struggle to move or cut through the grass. On the other hand, if the NET FORCE is too high, the lawnmower may move too quickly and not cut the grass evenly.

4. Can the NET FORCE on a lawnmower be changed?

Yes, the NET FORCE on a lawnmower can be changed by adjusting the force applied by the person pushing it or changing the weight of the lawnmower. Additionally, using a different type of blade or adjusting the height of the blade can also affect the NET FORCE.

5. How can the NET FORCE on a lawnmower be calculated?

The NET FORCE on a lawnmower can be calculated by adding together all the individual forces acting on it, including the force of gravity, the force applied by the person, and any resistance from the environment. The direction and magnitude of the NET FORCE can then be determined using mathematical equations.

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