In the figure below, a 1.2 kg ball is connected by means of two massless strings
ID: 2139339 • Letter: I
Question
In the figure below, a 1.2 kg ball is connected by means of two massless strings to a vertical, rotating rod. The strings are tied to the rod and are taut. The tension in the upper string is 31 N.
In the figure below, a 1.2 kg ball is connected by means of two massless strings to a vertical, rotating rod. The strings are tied to the rod and are taut. The tension in the upper string is 31 N. What is the tension in the lower string? What is the speed of the ball? m/s What is the magnitude of the net force Fvecnet on the ball? N What is the direction of Fvecnet? (0 degree means radially inwards.)Explanation / Answer
a) T1 = higher string; T2 = lower string
By drawing a triangle, you see that:
T*cos(theta) is the vertical force acting on the string
T*sin(theta) is the horizontal force acting on the string
This theta is 60 degrees from the vertical pole.
Net Force Vertical = T1cos(theta) -T2cos(theta) - mg = 0
because the ball is not going up or down. so:
T1cos(theta) -mg = T2cos(theta)
Plug in and solve...I'm not going to do that here.
B) You're asked to find V. So use centripetal forces equation:
Net force centripetal = mv^2/r = T1sin(theta) + T2sin(theta).
R = (Length of rope)*sin(theta)
So solve for v now.
C) Net forces that don't cancel out are centripetal forces. So then net force is just T1sin(theta) + T2sin(theta).
D) Toward center of the ball's rotation