To solve this problem we will apply the concepts related to the Doppler Effect. The Doppler effect is the change in the perceived frequency of any wave movement when the emitter, or focus of waves, and the receiver, or observer, move relative to each other.
Mathematically it can be described as
Where,
v = Speed of sound
f' = Reflected frequency
f = Emitted Frequency
= Speed of the object
Assuming that the speed of the medium is the speed of sound of 343m / s, we will then have that:
Answer:
175.3 N
Explanation:
The motion of the ball is a uniform circular motion, therefore the net force on it must be equal to the centripetal force.
There are two forces acting on the ball at the lowest point of motion:
- The tension in the string, T , upward
- The weight of the ball, , downward
The net force (centripetal force) has the same direction as the tension (upward, towards the centre of the circular path), so we can write:
where the term on the right is the expression for the centripetal force, and where:
T is the tension in the string
is the weight of the ball
is the mass of the ball
v = 5.7 m/s is the speed of the ball at the lowest point
r = 4.4 m is the length of the rope, so the radius of the circle
Solving for T, we find the tension in the string: