AP Physics Problem: Find Height on Icy Hill w/ 40km/h & 0.153 FK

In summary, the problem involves a car with a speed of 40.0 km/h approaching an icy hill with an angle of inclination of 10.5 degrees. The driver applies the brakes, causing the car to skid up the hill. The coefficient of kinetic friction between the ice and tires is 0.153. To determine how high the car will end up on the hill when it comes to rest, the equations of motion are used. The correct equation for acceleration should be -g(sinθ+fkcosθ), taking into account the forces of friction and gravity acting in opposite directions.
  • #1
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Homework Statement


A car with a speed of 40.0 km/h approaches the bottom of an icy hill. The hill has an angle of inclination of 10.5 degrees. The driver applies the brakes, which makes the car skid up the hill. If the coefficient of kinetic friction between the ice and the tires if 0.153, how high, measured along the incline, is the car on the hill when it comes to rest?

vi=40.0km/h=11.1m/s^2
theta=10.5 degrees
fk=0.153


Homework Equations




The Attempt at a Solution


-a=g(sinθ-ϥkcosϴ)
a=-.31m/s^2

vf^2-Vi^2/2(a)
=198.7m
 
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  • #2
-a=g(sinθ-ϥkcosϴ)
shouldn't it be:
a = -g(sinθ+fkcosθ)?
both forces points in opposite direction of initial velocity. So if you choose initial velocity to be (+) direction along hill, then acceleration due friction is negative and also due gravity is negative.
 
  • #3

Related to AP Physics Problem: Find Height on Icy Hill w/ 40km/h & 0.153 FK

1. How do I approach this AP Physics problem?

To solve this problem, you will need to use the equations for motion on an incline and the concepts of friction and kinetic energy. Start by drawing a diagram of the situation and labeling all known values. Then, use the equations and concepts to solve for the unknown height.

2. What is the equation for motion on an incline?

The equation for motion on an incline is: Fnet = ma = mgsinθ - μmgcosθ, where Fnet is the net force, m is the mass of the object, g is the acceleration due to gravity, θ is the angle of the incline, and μ is the coefficient of friction.

3. How do I find the coefficient of friction?

The coefficient of friction can be found using the equation: μ = Ff/N, where Ff is the frictional force and N is the normal force. In this problem, the normal force is equal to the weight of the object, which is given by mgsinθ.

4. Can I assume that the object is moving at a constant velocity?

Yes, since the problem states that the object is moving at a speed of 40km/h, we can assume that it is moving at a constant velocity. This means that the net force on the object is equal to zero and the equation can be simplified to: Fnet = mgsinθ - μmgcosθ = 0.

5. What is the final answer to this problem?

Using the equations and concepts, the final answer to this problem would be the height of the icy hill, which can be calculated by rearranging the equation for motion on an incline to solve for h: h = (v^2/2g)(1 + μtanθ), where v is the initial velocity (40km/h) and g is the acceleration due to gravity (9.8m/s^2).

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