How Does the Force to Start and Maintain Car Movement on Asphalt Differ?

In summary, to begin to drag a car with locked brakes on dry asphalt, a force of 1800 N is needed, calculated using the static coefficient of friction. To keep the car sliding, a force of 1440 N is needed, calculated using the kinetic coefficient of friction. This shows that a greater force is needed to start the car sliding compared to the force needed to keep it sliding. This is because the static coefficient of friction is higher, requiring a larger force to overcome the initial static friction and start the car moving.
  • #1
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Homework Statement



A car of weight 1500 N has its brakes locked. Calculate the force needed to begin to drag he car on dry asphalt. How will the force needd to slide it along the asphalt compare with the force needed to start sliding it? Why? (Static coefficient=1.2, Kinetic coefficient=0.8)

Known: weight (1500 N, the mass in N on earth) , coefficients of static and kinetic friction

Homework Equations



Ff = (coefficient of kinetic)(normal force)
Fn = mg

The Attempt at a Solution



(force needed to start it moving)
Force of friction = 1.2 * 1500 N
= 1800N

(force needed to keep it moving)
= Force of friction * coefficient Kinetic friction
= 1800N * 0.8
= 1440N

Now that I have these numbers, I do not know what to write to answer the questions that are asked.
 
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  • #2
I don't understand why you did 1800*0.8 for the second part. Should it not be 1500*0.8?

Ffr=uFN
 
  • #3
These numbers tell you that you need a greater force to get the car sliding than you need to keep it sliding.
 

FAQ: How Does the Force to Start and Maintain Car Movement on Asphalt Differ?

1. What is the definition of friction force?

The friction force is a contact force that opposes the relative motion or tendency of motion between two surfaces in contact. It is caused by the microscopic irregularities on the surface of the objects in contact.

2. How is the force of friction calculated?

The force of friction can be calculated using the formula F = μN, where F is the force of friction, μ is the coefficient of friction, and N is the normal force between the two surfaces in contact.

3. What factors affect the force of friction?

The force of friction is affected by the nature of the surfaces in contact, the normal force between the surfaces, and the coefficient of friction. Other factors such as the temperature, roughness, and speed of the surfaces also affect the force of friction.

4. What is the difference between static and kinetic friction?

Static friction is the force that prevents two surfaces from sliding past each other when there is no relative motion between them. Kinetic friction, on the other hand, is the force that opposes the motion of two surfaces when there is relative motion between them.

5. How can the force of friction be reduced?

To reduce the force of friction, one can use lubricants, such as oil or grease, between the surfaces in contact. Smoother surfaces and reducing the normal force can also decrease the force of friction. Additionally, using wheels or rollers can also reduce friction by changing the direction of the applied force.

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