Applications of Centripetal Force
A. Forces on a banked curve
Topics Covered:
- Going around a curve
- Road Design: banking avoids skidding
- Friction & Centripetal Force
- The Centrifuge and the Salad Spinner
Going Around Curves
Example:
A 4000 kg truck rounds a curve at 20 m/s. The radius of the curve is 100 m and the coefficient of friction on dry pavement (µ) is 0.6.
Find:
a) Fnet (The Net Force)
b) Ff (The Maximum Force of Friction)
c) if the truck will skid when µ = 0.15 (icy conditions)
Solution:
a) Fnet = Fc
= 16 000 N
b) 
= 23 520 N
c) When µ = 0.15, the force of friction is Ff = µ (m)(g) = 5 880 N
Note that the force of friction in this case is less than net Force. When this happens skidding will occur.
In general, to avoid skidding when going around a curve, the following condition must be satisfied:
Ff > Fnet
Other applications of Centripetal Forces include:
The Centrifuge
This a machine used to separate small particles suspended in fluids by spinning test tubes containing the suspensions at very high speeds. The larger particles separate first because they receive a larger component of the centripetal force that the smaller particles and thus are collected at the bottom of the test tube.
The Salad Spinner
This is a kitchen utensil used to dry your salad after you wash it.
The spinner has a basket with large holes that fits inside a slightly larger container. T
he container has a lid with a handle and a gear mechanism that hooks onto the inside of the basket.
When you turn the handle , the basket spins inside the container.
You put the wet salad in the basket, close the lid and spin it fast. a few seconds later you remove the lid and the salad is dried inside the basket.
The water that was on the lettuce leaves now collects at the bottom of the container.
The spinning action separates the water from the lettuce leaves by centripetal force.
The water is heavier than the lettuce and therefore receives a larger component of the centripetal force. [Fc is proportional to m]
Therefore the water's centripetal acceleration is larger than the salad's and it separates from the salad's leaves under gravity.
The basket traps the dry salad and prevents it from flying off.
