Circular Motion

[sous la pluie]

I am struggling with physics in general because I totally understand all the formulas and can constantly get the right numbers but I am useless when it comes to physics theory and that is very problematic. My teacher is very math inclined so he teaches us how to sole problems very well but I rarely learn anything about why this or that works in his class. Right now we are studying circular motion and I just fail to understand the acceleration concept. I know that if something moves in a circle, it accelerates towards the centre, just as the centripetal motion of the object also goes towards the object but WHY??

The acceleration aspect in particular boggles my mind but I don't fully understand why the net/centripetal force is towards the centre either. Any help would be greatly appreciated.

[Drake Glau]

It's the vector's fault. If you take the velocity of one of the objects at 2 points on the circle you get two different lines that go in different directions (think free body diagram). Keeping speed constant mind you, so velocity is only changing direction.

http://hyperphysics.phy-astr.gsu.edu/hbase/cf.html#cf might help a bit.

The vectors can form a triangle which you find then use to measure the the arc distance change. This arc is also the change in your velocity (since it changed directions as it went around) but also points towards the inside because your two velocity vector sides, when connected to form the hypotenuse, are now pointing to the middle of the circle. Since your velocity changed and dV/dT=a=arc measurement, your acceleration is in that same direction, towards the middle.

The force goes towards the middle also, but simpler to explain

f=ma

m stays constant, f stays constant, your a stays constant also, but your a is still pointing towards toward the middle which is pointing your force to the middle with it.

This is my super over simplified version that could quite possibly be wrong. Everything I said was based off that hyperphysics link though

[Guest Red XII]

As something moves around a circle, its velocity is always tangent to the circle (because its velocity is in its current direction of the motion). As the object goes around the circle, this tangent changes direction so that it's still a tangent. To do that, it has to turn in towards the circle. The acceleration is what's keeping the object going in a circle instead of off in a straight line, so it has to be turned towards the middle of the circle because the object's velocity would otherwise cause it to move in a straight line tangential to the circle from wherever it is (which is what happens if the centripetal force stops acting on the object).

[Guest Deven Kothari]

Do physics SL students need to learn about angular velocity?

I know about centripetal frce, velocity etc.. but Angular velocity, do we have to learn that?

[puyol9]

Yes, SL physics needs to know what angular velocity is.

It took me awhile to work it out, and its name is confusing. Basically velocity is the change in something per time unit (second), thus angular velocity is the change in the angle per time unit (second). Its units are rads s^-1.

Angular velocity is NOT the same as angular frequency. Angular frequency is the same as angular speed, that is to say, both angular frequency and angular speed are a scalar quantity of the magnitude of angular velocity (a vector quantity). The differences between angular velocity and angular frequency/speed are thus basically the same as the differences between normal velocity and normal speed.