need some help with mechanics (1 Viewer)

[vds700]

were doing conical pendulum atm and im really struggling with the questions in the fitzpatrick book. There are some examples but they are not very clearly explained. My problem is mainly just working out the vertical and radial force equations. Just wondering if anyone had any tips on that.

Also, does the terry lee 4 unit textbook cover mechanics well aand is it worth getting at this stage?

 

[Affinity]

The usual algorithm is:
identify forces acting on the particle, this should be a complete list (I hope):

1. Gravity
2. Normal reaction force
3. Tension
4. Friction/resistance

then fill in those you know and put an arrow and a letter in for those you don't.

gravity is straight forward... usually constant downwards.

the other 3 are not so straightforward as they vary
for example for a conical pendulum the tension T varies so that it's vertical component will match gravity/ Somehting similar holds with banked tracks.

once you identify each force you just need to resolve it into vertical and horizontal components by using a right angled triangle. the force vector is always the hypotenuse (just remember that the vertical and horizontal components of a force cannot be greater than the force itself.

Then you sum up each of the components so you get a resultant force acting on the particle in each direction. Then you match this with the force required to maintain the movement in the way prescribed.

for example if you have a conical pendulum, the horizontal component should = v^2/r = rw^2 inwards (to keep it going in a circle). an the vertical component should be zero (to keep it at the same height)




I reckon Fitzpatrick is ok.. people say it's easy though. If you have time go through material that is not specifically for the HSC, I found that useful as it makes ppl think instead of going into auto pilot (because they had drilled the methods in)

 

[vds700]

The usual algorithm is:
identify forces acting on the particle, this should be a complete list (I hope):

1. Gravity
2. Normal reaction force
3. Tension
4. Friction/resistance

then fill in those you know and put an arrow and a letter in for those you don't.

gravity is straight forward... usually constant downwards.

the other 3 are not so straightforward as they vary
for example for a conical pendulum the tension T varies so that it's vertical component will match gravity/ Somehting similar holds with banked tracks.

once you identify each force you just need to resolve it into vertical and horizontal components by using a right angled triangle. the force vector is always the hypotenuse (just remember that the vertical and horizontal components of a force cannot be greater than the force itself.

Then you sum up each of the components so you get a resultant force acting on the particle in each direction. Then you match this with the force required to maintain the movement in the way prescribed.

for example if you have a conical pendulum, the horizontal component should = v^2/r = rw^2 inwards (to keep it going in a circle). an the vertical component should be zero (to keep it at the same height)




I reckon Fitzpatrick is ok.. people say it's easy though. If you have time go through material that is not specifically for the HSC, I found that useful as it makes ppl think instead of going into auto pilot (because they had drilled the methods in)

Thanks! This was very helpful.

 

[shinn]

Also, in a one string system the tension forces are equal on the string whilst in system with more than one string, the tension forces are unequal.