# Help with high school dynamics assignment?

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1. Mar 12, 2015

### parabola

< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >

I've searched for help before posting, found this thread that is asking for the same assignment by unfinished so I'll just copy and paste lol

A 1000-kg car moves at a maximum speed so that it does not skid off the 50-m radius level track. If the coefficient of static friction between the road and wheels is 0.80. What is the maximum speed? Assume that the gravitational constant is 10.0 N/kg =10.0 m/s. Use the simulations in 4.5 Car Circles a Track to check your answers.

Write an equation for the vertical y-component form of Newton's second law. Determine the magnitude of the normal force. Then use a force law equation to determine the magnitude of the static friction force.

Write an equation for the radial component form of Newton's second law. Use this to determine the maximum speed that the car can travel so that it does not skid (so that friction can provide the needed force to keep the car moving in a circle). Once you have calculated the maximum speed adjust the speed slider in the 4th simulation to this speed and see if the car stays on the track.

The person that helped said it would be 8000 newts. I get 80 000 because I multiplied f(n) i did f(static)=msfn. Where did I go wrong?

Last edited by a moderator: Mar 12, 2015
2. Mar 12, 2015

### BiGyElLoWhAt

Welcome Parabola (math or tool?)
I have no idea what msfn is, or anything else in that equation, if you'd be so kind as to clear up what you're trying to do, it would make it easier to help.

3. Mar 12, 2015

### parabola

Thank you for responding. I did my question properly since I posted in the wrong area the first time.

1. The problem statement, all variables and given/known data

http://media.pearsoncmg.com/bc/aw_y...edia/CircularMotion/CarCirclesTrack/Main.html

Question 1

The 1000kg car is moving at the maximum speed it can without skidding off the 50m-radius level track. If the coefficient of static friction between the road and wheels is 0.80, what is this maximum speed? Assume that the gravitational constant is 10.0N/kg = 10.0m/s2

Question 2
Force Diagram
Construct a force diagram for the car when it has gone halfway around the track. Assume the car is moving and draw the diagram as seen from the front of the car. The center of the track is toward the right, and the sky is upward on the screen.

Question 3
Newton's Second Law (vertical y-component form)
Write an equation for the vertical y-component form of Newton's second law. Determine the magnitude of the normal force. Then use a force law equation to determine the magnitude of the static friction force.

Question 4
Newton's Second Law (radial component form)
Write an equation for the radial component form of Newton's second law. Use this to determine the maximum speed that the car can travel so that it does not skid (so that friction can provide the needed force to keep the car moving in a circle).

2. Relevant equations

f=ma
f=mvsquared/ r

3. The attempt at a solution

Sorry if not clear I meant I used force normal + static friction for force in the x direction. i used ms to mean the coefficient of static fric.

And my username is from both, that video still gives me the heebie jeebies and I seen it when i was like 7. lol

4. Mar 12, 2015

### BiGyElLoWhAt

Not plus, times, right? $F_N*\mu_s$ ?

5. Mar 12, 2015

### parabola

yes times!

6. Mar 12, 2015

### BiGyElLoWhAt

So where does this 80000N come from?

7. Mar 12, 2015