Minimum amount of friction in a turn

[TheronSimon]

Homework Statement

What minimum coefficient of friction between the tires and the road will allow a 3700 kg truck to navigate an unbanked curve of radius 25 m at a speed of 45 km/h?

Homework Equations

The Attempt at a Solution

The minimum coefficient is 7.62. To arrive at this i used the formula k(min)=(V²/(gr)). This will be substituted to 25²/(3700/45).

 

[Doc Al]

Your formula is correct, but your substitution is not. Hint: Convert the speed to standard units of m/s.

 

[TheronSimon]

so instead put in 12.5, and then 625/296 = 2.11 ?

 

[Doc Al]

so instead put in 12.5, and then 625/296 = 2.11 ?

No. Where do the numbers 625 and 296 come from?

 

[TheronSimon]

well 25^2 is 625 and 3700/12.5 is 296

 

[Doc Al]

well 25^2 is 625 and 3700/12.5 is 296

You need to evaluate: (V²)/(gr)

No need to square 25 or involve 3700.

 

[TheronSimon]

you lost me now, why would i square V^2? :(

 

[Doc Al]

you lost me now, why would i square V^2? :(

See your first post. (You need to evaluate V^2, which is V squared.)

To arrive at this i used the formula k(min)=(V²/(gr)).

 

[TheronSimon]

but i thought it would only SQRT if both sides have an exponent of 2 to get rid of the 2, because what i do to one side i have to do to the other do i not?