Slightly harder - pushing a lawnmower against friction

  • Thread starter Adama0905
  • Start date
  • Tags
    Friction
In summary, the problem involves a 22-kg lawnmower with a 35 degree angle between the handle and the ground. The coefficient of friction is .68 and the question asks for the magnitude of force needed to push the mower at constant velocity in the direction of the handle. The solution provided is 342 N, but after using the equation Fstatic = (mu)*(Forcenormal), the calculated force is 146.6 N. It is then realized that the hypotenuse of the force triangle must be found, leading to a final answer of 178.9 N, which is half of the correct answer. Help is requested in finding the mistake.
  • #1
Adama0905
3
0

Homework Statement


The handle of a 22-kg lawnmower makes a 35 degree angle with the horizontal. If the coefficient of friction between lawnmower and ground is .68, what magnitude of force is required to push the mower at constant velocity? Assume the force is applied in the direction of the handle.


Homework Equations



Fstatic = (mu)*(Forcenormal)

The Attempt at a Solution



Okay, so this problem comes with a solution at the back of the book. Says 342 N. Well, I thought about this logically, and said that the Force to get this thing going will have to be equal to the mu times the Forcenormal, that's what will have to be overcome. So I did that and got 146.6 Newtons. Well, it makes a 35 degree angle to the ground, so that is only the horizontal force we need. If we're pushing on the handle, I have to find the hypotenuse of that force triangle, and I got 178.9 Newtons, roughly half of the right answer. What am I doing wrong?
 
Physics news on Phys.org
  • #2
If I'm pushing on the handle, I should be finding the hypotenuse. What am I missing? I must be missing something. Please help, if you can.
 
  • #3


Your approach is correct, but you may have made a calculation error. Let's break it down step by step:

1. Determine the normal force: The normal force is the force exerted by the ground on the lawnmower in the opposite direction of gravity. In this case, it is equal to the weight of the lawnmower, which is 22 kg * 9.8 m/s^2 = 215.6 N.

2. Determine the frictional force: The frictional force is equal to the coefficient of friction (mu) times the normal force. In this case, it is 0.68 * 215.6 N = 146.6 N.

3. Determine the horizontal force: This is the force that needs to be applied to overcome the frictional force. It is equal to the frictional force, 146.6 N.

4. Determine the total force: This is the hypotenuse of the force triangle, which is equal to the square root of the sum of the squares of the horizontal and vertical forces. In this case, it is equal to sqrt(146.6^2 + 146.6^2) = 207.5 N.

So the correct answer is actually closer to your initial calculation of 178.9 N, but slightly higher due to rounding errors. The book's answer of 342 N may be incorrect.
 

1. How does friction affect the pushing of a lawnmower?

Friction is a force that resists the motion of two surfaces rubbing against each other. When pushing a lawnmower, the friction between the wheels and the ground can make it harder to move the mower forward.

2. Can the weight of the lawnmower affect the amount of force needed to push it?

Yes, the weight of the lawnmower can affect the amount of force needed to push it. The heavier the lawnmower, the more force is required to overcome the friction between the wheels and the ground.

3. How can I reduce the effects of friction when pushing a lawnmower?

One way to reduce the effects of friction when pushing a lawnmower is to regularly lubricate the wheels and axles. This will reduce the amount of resistance between the mower and the ground, making it easier to push.

4. Does the type of surface affect the amount of friction when pushing a lawnmower?

Yes, the type of surface can affect the amount of friction when pushing a lawnmower. For example, pushing a lawnmower on a smooth, paved surface will require less force than pushing it on a rough, uneven surface.

5. Is it better to push a lawnmower with more force or at a slower pace?

It is better to push a lawnmower with a steady, moderate amount of force rather than pushing with excessive force or at a slower pace. Pushing too hard can cause fatigue and pushing too slowly can make it harder to overcome the effects of friction.

Similar threads

  • Introductory Physics Homework Help
Replies
3
Views
989
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
18
Views
12K
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
3K
  • Introductory Physics Homework Help
Replies
7
Views
2K
  • Introductory Physics Homework Help
Replies
8
Views
2K
  • Introductory Physics Homework Help
Replies
16
Views
2K
  • Introductory Physics Homework Help
Replies
1
Views
7K
  • Introductory Physics Homework Help
Replies
7
Views
2K
Back
Top