Ok this will be a long post, sorry in advance. I am an online student of a university and the help I am getting from them is ridiculous, I am also using a book called quicksmart introductory physics, and for the most part it is quite rubbish.
1st Problem: (not homework questions, I am trying to figure out the example and how it works)
http://postimage.org/image/wfk1kp6jx/ scan of the page
If you can see that scan of the page, great. It is about two masses on a pulley/string and one mass is on an incline. I can work out the acceleration of the seperate masses (g for straight down, g x Sinθ for the incline) and that F=ma.
I am having trouble understanding how to get the resulting acceleration of the masses (I seem to have no trouble when it is a matter of two objects straight down on a string/pulley with different masses). As well as I can not figure out the Tension either.
I really need a simple explanation of how to do this process, as the book just goes from easy enough physics to all this overdrive in this example.
2nd Problem:
Short story, 2 mass on a pulley both directed at the ground. resulting in a 20kg mass accelerating towards the ground at 5.88m/s/s and has 2m to fall.
The acceleration part i worked out easy enough, but the time to calculate it to move those 2m i cant get it.
i used s=ut+0.5a(t^2)
rearranged it to get t^2 = 2.944/2
t = 1.21s
however this is apparantly wrong and the book answers says a formula t^2 = 2s/a
t = 0.82s
where did this come from?
the resulting velocity i got from a = v/t so i mistakingly went v = a/t which ironically gave me the right answer for v (but i had t wrong).
v = at provides the right answer if t is right.
So why doesnt my first formula work for t?
Problem 3:
car 1 is travelling at a constant 30m/s and is 50m ahead of a stationary car 2.
car 2 uniformly begins accelerating at 4m/s/s. when will the car catch up?
The book gives me no information at all how to work this out.
The solution gives 50 +30t = 0 + 1/2 x 4t^2
I can see this is a modified s = ut + 0.5at^2 but I have no idea how it works or how to get to it?
Thanks if i can get just a little help understanding this!!
1st Problem: (not homework questions, I am trying to figure out the example and how it works)
http://postimage.org/image/wfk1kp6jx/ scan of the page
If you can see that scan of the page, great. It is about two masses on a pulley/string and one mass is on an incline. I can work out the acceleration of the seperate masses (g for straight down, g x Sinθ for the incline) and that F=ma.
I am having trouble understanding how to get the resulting acceleration of the masses (I seem to have no trouble when it is a matter of two objects straight down on a string/pulley with different masses). As well as I can not figure out the Tension either.
I really need a simple explanation of how to do this process, as the book just goes from easy enough physics to all this overdrive in this example.
2nd Problem:
Short story, 2 mass on a pulley both directed at the ground. resulting in a 20kg mass accelerating towards the ground at 5.88m/s/s and has 2m to fall.
The acceleration part i worked out easy enough, but the time to calculate it to move those 2m i cant get it.
i used s=ut+0.5a(t^2)
rearranged it to get t^2 = 2.944/2
t = 1.21s
however this is apparantly wrong and the book answers says a formula t^2 = 2s/a
t = 0.82s
where did this come from?
the resulting velocity i got from a = v/t so i mistakingly went v = a/t which ironically gave me the right answer for v (but i had t wrong).
v = at provides the right answer if t is right.
So why doesnt my first formula work for t?
Problem 3:
car 1 is travelling at a constant 30m/s and is 50m ahead of a stationary car 2.
car 2 uniformly begins accelerating at 4m/s/s. when will the car catch up?
The book gives me no information at all how to work this out.
The solution gives 50 +30t = 0 + 1/2 x 4t^2
I can see this is a modified s = ut + 0.5at^2 but I have no idea how it works or how to get to it?
Thanks if i can get just a little help understanding this!!