Circular Motion (1 Viewer)

[ezzy85]

Which formulae can we learn and use in the exam and which ones do we have to prove? if they ask for a centripetal force, can I just put down F=mv²/r and the same with accelaration?

Also, if they say find the speed, do you assume theyre talking about tangential or angular?

And now a question from Arnold...

A mass of 1kg is fastened by a string of length 1m to a point 0.5m above a smooth horizontal table and is describing a circle on the table with uniform angular speed of 1 rev in 2 seconds. Find the force exerted on the table.

Im having trouble picturing it. Is it a pendulum?

Thanks

 

[Fosweb]

Diagram.

 

[Avicenna]

Originally posted by ezzy85
Which formulae can we learn and use in the exam and which ones do we have to prove? if they ask for a centripetal force, can I just put down F=mv²/r and the same with accelaration?

Also, if they say find the speed, do you assume theyre talking about tangential or angular?

And now a question from Arnold...

A mass of 1kg is fastened by a string of length 1m to a point 0.5m above a smooth horizontal table and is describing a circle on the table with uniform angular speed of 1 rev in 2 seconds. Find the force exerted on the table.

Im having trouble picturing it. Is it a pendulum?

Thanks

hey ezzy if they ask for the speed of the object then i would assume that they're asking for its tangential velocity or speed. if however they ask you for its angular velocity then you give them the value of "w"......

as for that arnold mechanics questiopn yes it is a conical pendulum in which the object is describing a circle on the table.....unlike the usual pendulum questions where the object is producing a circle in the air, here the table produces a reaction force N which balances the mg force of the object .... also draw a free-body diagram of this scenario and put in all the forces acting on the object, this always helps.

also remember to change the revs/ second to rad/sec by multiplying the revs by 2pi and then dividing it by 2 two obtain the angular speed in rads/sec not rads/ 2 seconds


Good luck solving the question

 

[ezzy85]

thanks guys
i didnt think it was a pendulum because thats in the next chapter. this chapter was only supposed to be with regular uniform motion.

 

[Newbie]

heres my question
we have about 4 lessons left to finish half of circular motion and then harder 3unit

is it possible?

 

[underthesun]

Of course it's possible, if no-one asks for questions

 

[Newbie]

we are sooo doomed