Uniform Circular Motion of a tire

[Muneerah]

Homework Statement

A point on the outer rim of a tire on a moving
vehicle exhibits uniform circular motion with
a frequency of 28 Hz. The diameter of the tire
is 40 cm.
How fast is the car moving?
Answer in units of km/hr.

Homework Equations

V=2 pi r f

The Attempt at a Solution

The first thing I did was finding the frequency in terms of hrs, and I got 100800 revelotions per hr. Then I found converted the radius to km so I got .0002 km. Then I found the velocity which is, 2 pi r f = 126.669 km/hr. My answer is wrong, I don't know what it is that I did wrong so if you can please help. Thank you

 

[xcvxcvvc]

Homework Statement

A point on the outer rim of a tire on a moving
vehicle exhibits uniform circular motion with
a frequency of 28 Hz. The diameter of the tire
is 40 cm.
How fast is the car moving?
Answer in units of km/hr.

Homework Equations

V=2 pi r f

The Attempt at a Solution

The first thing I did was finding the frequency in terms of hrs, and I got 100800 revelotions per hr. Then I found converted the radius to km so I got .0002 km. Then I found the velocity which is, 2 pi r f = 126.669 km/hr. My answer is wrong, I don't know what it is that I did wrong so if you can please help. Thank you

I'm getting the same answer. If I had to guess, your book/teacher probably miscalculated or had a typo.

 

[kerimek]

Hello,

It seems that you have made a small mistake in your calculation. When converting the radius to km, you should have gotten 0.0004 km instead of 0.0002 km. This is because the diameter of the tire is given to be 40 cm, which is equivalent to 0.4 m. When converting to km, you need to divide by 1000, so you should get 0.0004 km.

Using this corrected value for the radius, your final answer for the velocity should be 253.338 km/hr.

I hope this helps. Keep up the good work!