Centripetal force (1 Viewer)

[darkwarrior2]

Question 18 from 2004 hsc. http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2004exams/index4.html#p

In the car turning, is the frictional force of the car and the tyres = to the centripetal force?
Also, how do i show using the numerical data that the statement is incorrect? i can find the centripetal force but what do i equate this with?
This question completely baffles me :/

 

[rama_v]

The statement is incorrect. The tyres provide the centripetal force required to sustain the ciruclar motion. Without a force acting inwards the car would just be travelling in a straight line, at a tangent to the circle.

Also since the car is changing velocity (its direction is changing), this means it is accelerating. Hence Newton's second Law F = ma states that when an object is accelerating, it is experiencing a force. In this case, F = ma but a = v²/r
So The net force on the car is F = mv²/r ...Just sub in the numbers - this proves that there is a net force acting on the car.

This website was of paticular help to me in understanding th concepts described above:
http://www.glenbrook.k12.il.us/gbssci/phys/Class/circles/u6l1c.html

 

[darkwarrior2]

thanks

so basically there is no need for balancing of any forces, because i was confused in thinking that there was a force acting to the right of the car, outward and that i needed to balance these two forces.
so just show that Centripetal force IS the net force acting on the car and that the friction of the tyres + road provides this centripetal force. thanks

 

[rama_v]

There is only one force acting on the car (ignoring gravity - its balanced by the normal reaction force). It is the centripetal force provided by the car's tyres, that acts inwards towards the centre of the roundabout.

Whenever forces are unbalanaced there must be an acceleration of some sort occurring. In this case the acceleration is centripetal

EDIT: Thanks Helper

 

[helper]

Velocity is not a force.
In the answer you have given, remove the friction the car will continue forward due to Inertia. Inertia is not a force. Newton's 1st Law is what you are describing.

If velocity was a force, then its units would be Newton's and the result would be as you said it would accelerate, which it doesn't if you remove the friction.

 

[rama_v]

Velocity is not a force.
In the answer you have given, remove the friction the car will continue forward due to Inertia. Inertia is not a force. Newton's 1st Law is what you are describing.

If velocity was a force, then its units would be Newton's and the result would be as you said it would accelerate, which it doesn't if you remove the friction.

ooopps
will change it lol
I better read up on forces again