# Search results

1. ### Force of friction in circular motion

I'm having trouble with the following problem: If a curve of radius 80.0 m is perfectly banked for a car moving 70.0 km/hr, what must be the coefficient of friction in order to prevent skidding when the car is moving at 90.0 km/hr. OK, I know that I need to find the angle of the "perfectly...
2. ### Circular Motion and coefficient of static friction

I've been having trouble with the following problem: A curve of radius 60 m is banked for a design speed of 100 km/hr. If the coefficient of static friction is .30, at what range of speeds can a car safely make the curve? Here's what (I think) I know: We know that there are two forces...
3. ### Tire Marks

That's exactly where I was going wrong. For some reason, I kept solving the problem as if the car were accelerating, not decelerating. Thank you both for your help.
4. ### Tire Marks

I'm a bit confused as to how to finish this problem: At an accident scene on a level road, inestigators measure a car's skid marks to be 88 m long. It was a rainy day and the coefficient of friction was estimated to be .42. Use these data to determine the speed of the car when the driver...
5. ### How to incorporate the initial vellocity

I got it! I've been making such a dumb mistake. When I used v^2=u^2 + 2as, I kept forgetting to square the 13! Now I'm getting the right answer. Thanks a lot for helping me out here.
6. ### How to incorporate the initial vellocity

ok, so that gives an acceleration of 2.32m/s^2. But it doesn't make sense that this would be the acceleration to plug into the formula F=ma. I know that the correct answer to the problem is 210 N.
7. ### How to incorporate the initial vellocity

what do the variables stand for?
8. ### How to incorporate the initial vellocity

I'm having difficulty with the following problem: What is the average force exerted by a shot-putter on a 7.0 kg shot if the shot is moved through a distance of 2.8 m and is released with a speed of 13 m/s. I know that I have to use the formula F=ma. The mass is obviously 7.0 kg, but I don't...
9. ### If a rock is dropped off a sea cliff

Thanks for the help. As I said before, my difficulty lay in not being able to start the problem, and now I know where I must begin. Thanks again for helping me out.
10. ### If a rock is dropped off of a sea cliff

Thank you very much for the help; your idea of creating the equation v1+ v2 = 3.4 is exactly what I needed to finish the problem off. I hadn't previously thought about solving the equations silmultaneously like that.
11. ### If a rock is dropped off of a sea cliff

If a rock is dropped off of a sea cliff, and the sound of the rock hitting the water is heard 3.4 seconds later, how tall is the cliff, assuming the speed of sound is 340 m/s. What I've been trying to do is break the problem up into 2 parts, one for the rock going down towards the sea, and one...
12. ### If a rock is dropped off a sea cliff

If a rock is dropped off a sea cliff, and the sound of it striking the water is heard 3.4 seconds later, how high is the cliff, assuming the speed of sound to be 340 m/s. I don't really know where to begin with this one, and I would really appreciate the help. Thanks.