Question

Hi I NEED HELP WITH UNDERSTANDING THE LANGUAGE OF THIS QUESTION. I KNOW THE SOLUTION BUT I DONT GET HOW TO SOLVE IT.

An object is constrained by a cord to move in a circular path ofradius 0.5m on a horizontal frictionless surface. The
cord will break if its tension exceeds 16N. The maximum kineticenergy of the object can have is:

Answer 1

I have a final exam this week. Anyone please help me ASAP.

Answer 2

So if something is moving in a circular fashion, what do you know about it's acceleration?

Answer 3

it equals v^2/R

Answer 4

yup yup ^_^ And what is/are the force/s that are acting on the object?

Answer 5

tension

Answer 6

and I thought there was also gravity (mg) but when I looked at the solution, it turns out there is only tension

Answer 7

that is actually the part that I need help with

Answer 8

Well, gravity is acting on the object, but it only exerts a force downwards. If the table were not frictionless, that you would have to use the force of gravity to find the normal force of the object - however, in any case, gravity works perpendicularly to the force the tension of the rope supplies, and so does not contribute to the sum of forces in that direction. All you're left with on the horzontal surface is

\[\sum F = T ≤ F_{net}\]
and your net fore is the mass times the centripetal acceleration, so
\[ T ≤ ma_{cent}\]
\[ T ≤ m\frac{v^2}{r}\]

Answer 9

oh ok I get it now

Answer 10

cool cool ^_^

And you know the formula for kinetic energy and such?

Answer 11

is it ok if you draw me a picture of the question as well?

Answer 12

yes actually. I know how to do the rest of the problem.

Answer 13

then why does it say "horizontal" surface?

Answer 14

That's looking down at it from the top

Answer 15

or mayby the picture is like this