What is the Frictional Force Acting on a Block on a Rough Incline Plane?

In summary, a 10kg block is released on a 30 degree incline plane and accelerates down at 2m/s^2. The kinetic friction force acting on the block is 30N. The coefficient of friction was incorrectly calculated using 2/10 and needed to be adjusted for the non-planar surface of the incline.
  • #1
Priyadarshini
191
4

Homework Statement


A block of mass 10kg is released on a rough incline plane which is inclined at 30 degrees. Block start descending with acceleretion 2m/s^2. Kinetic friction force acting on the block is:
A) 10. B) 30. C) 50. D) 50*3^(1/2)

Homework Equations



f= meu*N
a=meu*g

The Attempt at a Solution


meu= 2/10=1/5
N=mgcostheta
= 50*3^(1/2)
frictional force= 50*3^(1/2) / 5
which is 10*3^(1/2) and is not in the options.
 
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  • #2
I think you should start off by determining the forces acting on the object first
Equate through forces, you don't even need to bring in the variable ##μ##
 
  • #3
Suraj M said:
I think you should start off by determining the forces acting on the object first
Equate through forces, you don't even need to bring in the variable ##μ##
50-friction=ma
50-friction= 20
f=30N
But why doesn't my initial working give me this answer?
 
  • #4
How did you get your coefficient of friction to be 1/5?
It's not in plane with the ground hence you can't just take 2/10 you have to take their components
 
Last edited:
  • #5
Suraj M said:
How did you get your coefficient of friction to be 1/5?
It's not planar with the ground hence you can't just take 2/10 you have to take their components
What do you mean by "planar with the ground"? The f=N*meu formula has conditions? I thought it could be applied to any situation.
 
  • #6
Which force will pull the block down and which force will oppose the motion? Draw FBD. As Suraj said earlier, you don't need μ.
 
  • #7
cnh1995 said:
Which force will pull the block down and which force will oppose the motion? Draw FBD. As Suraj said earlier, you don't need μ.
Thank you, the answer matched. However I do not completely understand why my initial method did not give me the same answer.
 
  • #8
Priyadarshini said:
What do you mean by "planar with the ground"? The f=N*meu formula has conditions? I thought it could be applied to any situation.
Not conditions Priyadarshini, your normal force is ?
You've taken 2/10
That denominator is the normal acceleration right? But that's not the normal acceleration in this case because the plane is not parallel to the ground
So you'll have to take a component of this.
FBD please
(PS- Look at us 3 Indians at this hour :-) sorry off subject- ignore this)
 
  • #9
Suraj M said:
Not conditions Priya, your normal force is ?
You've taken 2/10
That denominator is the normal acceleration right? But that's not the normal acceleration in this case because the plane is not parallel to the ground
So you'll have to take a component of this.
FBD please
PS- Look at us 3 Indians :-) sorry off subject- ignore this
Ohhh. I see! Thank you!
Haha, true. The name is Priyadarshini by the way, not Priya.
 
  • #10
Priyadarshini said:
Ohhh. I see! Thank you!
Haha, true. The name is Priyadarshini by the way, not Priya.
Sorry my bad, down here we just omit the "darshini"
No offence, force of habit
Hope you got your answer[emoji106]
 
  • #11
Suraj M said:
Sorry my bad, down here we just omit the "darshini"
No offence, force of habit
Hope you got your answer[emoji106]
None taken, a lot of people do that.
Yup, thanks a lot.
 
  • #12
mgsin(30)-friction = ma
10*10*(1/2) - friction = 10*2

friction = 30 N
 

1. What is frictional force?

Frictional force is a force that resists motion between two surfaces in contact. It is caused by roughness and irregularities on the surfaces, and it acts in the opposite direction of the intended motion.

2. How is frictional force calculated?

Frictional force is calculated by multiplying the coefficient of friction (a measure of how easily two surfaces slide past each other) by the normal force (the force that the surfaces exert on each other due to their weight or other external forces).

3. What are some real-life examples of frictional force?

Some real-life examples of frictional force include walking on the ground, rubbing your hands together, and using brakes on a bike or car to slow down or stop.

4. How can frictional force be reduced?

Frictional force can be reduced by using lubricants such as oil or grease, making surfaces smoother, or using wheels and bearings to reduce direct contact between two surfaces.

5. What are the effects of frictional force?

The effects of frictional force include the generation of heat, which can cause wear and tear on surfaces, and the reduction of speed and efficiency in systems that rely on motion.

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