PLEASE HELP

A ball of mass 0.250 kg on the end of 0.850 m long cord (ignorable mass) iS swung in a vertical circle.

Determine:

(a) the minimum speed the ball must have at the top of its arc so that it continues moving in a circle

(b) the tension in the cord at the bottom of the arc if the ball is moving at twice that speed

Question

PLEASE HELP

A ball of mass 0.250 kg on the end of 0.850 m long cord (ignorable mass) iS swung in a vertical circle.

Determine:

(a) the minimum speed the ball must have at the top of its arc so that it continues moving in a circle

(b) the tension in the cord at the bottom of the arc if the ball is moving at twice that speed

ulahlynn · Answer

hi my sister! :D

jfraser · Answer

i assume you mean for part a) what velocity it must have to keep moving in a circle. What you need to see is that the KE of the ball MUST EQUAL the PE of its height in order to keep moving in the circular path.

Set KE = PE$$\frac{1}{2}m*v^2 = m*g*h$$and solve for v

anonymous · Answer

oh okay, I get it. how about the tension? do we need to get the normal force and stuff?

anonymous · Answer

:)

jfraser · Answer

there is no normal force because the ball isn't in contact with a surface like a table. You need to find the centripetal force, which is equal to the tension in the rope. Using the velocity you found from part a), plug it into a formula so you can find F. Something like:$$F_c = m*a_c$$but since $a_c$ is the centripetal acceleration, we can substitute and get $$F_c = \frac{m*v^2}{r}$$

anonymous · Answer

oh sorry bout that. thankyou very much

anonymous · Answer

can I ask another one? :)

jfraser · Answer

no need to apologize, just have to pay attention to what all the formulas in physics mean

jfraser · Answer

sure. close this and ask another