Solving Kinetic Friction: Find Coefficient of Friction from Car Stop

AI Thread Summary
To find the coefficient of kinetic friction for a car that stops after traveling 40 meters from a speed of 20 m/s, the acceleration can be calculated using the formula a = (v^2 - u^2) / (2s), resulting in an acceleration of 5 m/s². The frictional force is balanced by the mass times acceleration, leading to the equation u_k * m * g = m * a. By simplifying, the coefficient of kinetic friction is determined to be u_k = a/g, which results in a value of 0.5. This calculation effectively demonstrates how to derive the coefficient of friction from the given parameters.
mels
Messages
2
Reaction score
0

Homework Statement



A car is moving with a speed of 20m/s when the brakes are applied. The wheels lock (stop spinning). After traveling 40m, the car stops. Determine the coefficient of kinetic friction between the tires and the road.

Homework Equations



Fk=uk x Fn

The Attempt at a Solution



I don't know how to encorporate the given into the equation !
 
Physics news on Phys.org
There's another equation you need, one that puts all the given data together.
 
You can apply simple formula...

calculate the acceleration 'a'... by
(square of final velocity)-(square of initial velocity)=2x a x distance

a=20x20/(2x40)
a=5

balance the force
uk x mass x g = mass x a
uk=a/g
uk=5/10=0.5
 
Last edited by a moderator:
okay thank you ! i really appreciate it :)
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'Collision of a bullet on a rod-string system: query'

Thread 'Collision of a bullet on a rod-string system: query'

In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Coefficient of Friction question for a cart going down a wooden ramp
Replies
18
Views
3K
Does coefficient of kinetic friction depend on speed?
Replies
16
Views
5K
How to find the coefficient of kinetic friction
Replies
4
Views
3K
Distance travelled by a car considering only air friction?
Replies
4
Views
2K
Stopping distances on a downward slope
Replies
3
Views
2K
How to use the coefficient of kinetic friction?
Replies
36
Views
4K
Kinetic energy & Conservation of energy
Replies
17
Views
2K
Calculating the coefficient of kinetic friction
Replies
3
Views
3K
How to find coefficient of friction *Without* mass?
Replies
3
Views
22K
Coefficient of kinetic friction between a car and the road
Replies
12
Views
4K

Hot Threads

Recent Insights

Back
Top