Physics Problem: Solving Friction Coefficient on Lawnmower

In summary, the conversation is about a physics test with two problems involving frictional coefficient. The first problem is about finding the acceleration of a lawnmower with an applied force of 80N at an angle of 40º and a frictional coefficient of 0.15. The conversation includes a diagram and calculations using SOH-CAH-TOA functions to find the vertical and horizontal forces, as well as the weight and normal force of the lawnmower. The calculated frictional force is 53N, but a discrepancy is noted as the lawnmower is not moving despite the applied force. The conversation ends with a suggestion to check the resolution of the 81N force into its components. The final calculated acceleration is
  • #1
Inspector Gadget
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I have a test in my physics class early this week, and there are two problems on the review sheet I am having problems getting...both of them having a frictional coefficient...

Here is the first one that I think I understand but the answer I'm getting doesn't exactly make sense...

PROBLEM: An 80N force is applied to the handle of a lawnmower. The handle makes an angle of 40º with the ground. If the coefficient of friction between the lawnmower and the ground is 0.15, find the acceleration of the 30kg lawnmower.

I've attached an image below and I'll explain what I have on it...everything in black is given information and what's in red I figured out, which I'll explain.

Using the SOH-CAH-TOA functions, I found that the vertical force was 61.3 N, and the horizontal force is 51.4 N, and our teacher has as round all forces in Newtons to the nearest whole number, so that's 61 N and 51 N.

Next, the downward force of the lawnmower is...
W=m*g=(30 kg)(9.8 m/sec²)=294 N

The normal / perpindicular force pushing up on the lawnmower has to be equal, so you have the 294N going down from the weight of the lawnmower, plus the 61N of downward force from pushing the lawn mower, that's 294N + 61N = 355N.

frictional force = (frictional coefficient)(normal force)=(.15)(355)=53N

There's a 51N force that we found from pushing the lawnmower pushing forward. But from what I found about, you need 53N to overcome friction, so I'm finding the lawn mower isn't even moving. Maybe what I did is right and it's true, but I'd like someone to just look over what I did and either correct or confirm.

Thanks in advance.
 

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  • #2
Your answer looks right to me. I'd say it wasn't going to accelerate from rest in the curretn configuration too.
 
  • #3
Check your resolving of the 81N force into its horizontal and vertical components, that's where ure mistake is.

I get the acceleration as approximately 0.31 m/s/s
 
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1. What is friction and how does it affect a lawnmower?

Friction is a force that occurs when two surfaces come into contact with each other. In the case of a lawnmower, friction occurs between the blades and the grass, which helps to cut the grass. However, too much friction can also make it difficult for the lawnmower to move forward, requiring more energy to push it.

2. How is the coefficient of friction calculated for a lawnmower?

The coefficient of friction is calculated by dividing the force required to move the lawnmower by the weight of the lawnmower. This value is then compared to the known coefficient of friction for similar surfaces to determine the exact value.

3. What factors can affect the friction coefficient on a lawnmower?

The friction coefficient on a lawnmower can be affected by various factors such as the type and condition of the blades, the type and condition of the grass, and the weight and design of the lawnmower. Additionally, environmental factors such as moisture and temperature can also impact the friction coefficient.

4. How can the friction coefficient be reduced on a lawnmower?

The friction coefficient on a lawnmower can be reduced by regularly sharpening and maintaining the blades, choosing a lawnmower with a lower weight and better design, and selecting a lawnmower with features such as a grass catcher or adjustable height that can help reduce the amount of friction.

5. Why is it important to know the friction coefficient on a lawnmower?

Knowing the friction coefficient on a lawnmower can help determine the amount of effort and energy required to operate it, as well as the effectiveness of the lawnmower in cutting grass. It can also help identify any potential issues or areas for improvement in the design or maintenance of the lawnmower.

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