In: Physics
A coin is moving in a horizontal circle in a cone. The cone has height 70 cm and radius 20 cm. The coin is at a height halfway up. The coefficient of static friction is 0.3. The mass of the coin is 5 g. How fast is the coin moving to stay at this height?If the velocity is halved what will the height of the coin be now?
In triangle ABC
tan = BC/AB
tan = r/h
tan = 20/70
tan = 0.286
=
tan-1(0.286)
= 16 deg
m = mass of coin = 5 g = 0.005 kg
us = Coefficient of friction = 0.3
fs = static frictional force = us Fn
Along the vertical direction, force equation is given as
Fn Sin + fs
Cos
= mg
Fn Sin + (us
Fn ) Cos
= mg
Fn = mg /(Sin + us
Cos
)
Fn = (0.005 x 9.8) /(Sin16 + (0.3) Cos16)
Fn = 0.087 N
Along the horizontal direction , force equation is given as
Fn Cos - fs
Sin
= m
v2/r
Fn Cos - us
Fn Sin
= m
v2/r
0.087 Cos16 - (0.3 x 0.087)Sin16 = (0.005) v2/0.20
v = 1.75 m/s