Ball, with a weight of 200 grams, tied to a string rotates around in a horizontal plane. Period of rotation is 2 seconds. What is the force (in N) which acts on the string? The length of the string is 0.5 meters.

The force on the string is composed of two components, the weight of the ball, fy=mg, and the centripetal force due to rotation, fx=mrω².

m=0.2 kg
r=0.5m
ω=2π/2s=π rad./s

Resultant force
=√(fx²+fy²)

I have a different interpretation of this problem. r is the radius of the circular path of what is in this case a conical pendulum, not the length of the string.

Let the string tension be T. Let the string angle from vertical be A. Let the period be P = 2s

T cos A = M g
T sin A = M V^2/R
= M*(2 pi)^2 R/P^2

T^2 = M^2 [g^2 + (2 pi)^4*(R^2/P^4)]

You can also solve for the angle A,

tan A= (2*pi)^2*R/(P^2/g)

which leads to

P = 2 pi sqrt[R/(g tanA)]
= 2 pi sqrt[R cosA/sinA]
= 2 pi sqrt(L cosA/g)

For an L = 0.5 m length string, with a period of P = 2s
L cosA/g = 1/pi^2 s^2

This leads to an impossible value for cos A, greater than 1

The problem is overdetermined and the input data are inconsistent. The period of a mass on a string 0.5 m long in a conical orbit cannot be as long as 2 seconds. The same applies to a plane pendulum of that length.

I agree that it is impossible.

My previous solution omitted the reduction of radius as the angular speed is decreased.

If L=length of the string,
and θ=angle of string with vertical,
then
tan(θ)=fx/fy
=m(l*sin(θ)ω²/mg
On simplicication,
cos(θ)=g/(Lω²)
=9.81/(0.5*π²)
=1.98 which is impossible

For the system to work, either the length has to be doubled, or the period reduced to 1.4 sec. or less

In short, the data from the question should be confirmed or revised.

To determine the force acting on the string, we can use the formula for centripetal force.

The centripetal force (Fc) is given by the equation:

Fc = (m * v²) / r

Where:
m = mass of the object (in kilograms)
v = velocity of the object (in meters per second)
r = radius of the circular path (in meters)

First, convert the given weight of the ball from grams to kilograms:
200 grams = 0.2 kilograms

Next, find the velocity (v) of the ball. The velocity can be calculated using the formula for the circumference of a circle:

C = 2 * π * r

Where:
C = circumference of the circular path
r = radius of the circular path

In this case, the radius (r) is equal to the length of the string, which is 0.5 meters. So:

C = 2 * π * 0.5 = π meters

The time period (T) of rotation is given as 2 seconds, which is the time taken to complete one revolution. The velocity (v) can be calculated as:

v = C / T = π / 2 = π/2 meters per second

Now we have the mass (m = 0.2 kg) and the velocity (v = π/2 m/s). We can substitute these values into the formula for centripetal force:

Fc = (m * v²) / r = (0.2 * (π/2)²) / 0.5 = (0.2 * (π² / 4)) / 0.5 = (0.05 * π²) / 2 = 0.025π² Newtons

So, the force acting on the string is approximately 0.025π² Newtons.