Glad to help. I'm going to go ahead and move this thread to the Homework Help forums, since it's about schoolwork. Let us know if you have follow-up questions. As always, it's best to show us as much of your work as possible, since we can often guide you better after we see how you are working out the problems.predicting motion course, struggling abit. i even worked out the spring constant on the question before. now its asking me to work out the speed which means combining equations at a guess. its an open university course, so alot of reading involved which doesn't suit me really. As soon as someone explains it in a different way i normally understand it. advice is good on here though!
Looking pretty good so far, but the units on K are not quite right. Should be N/m, not Nm. Double check that you worked the equation right, and check your units as you carry them along (and cancel them just like you do real numbers).everything......................!
its about a small toy attached to a spring with a suction device on the bottom.
the total compression of the spring is 1.2 cm
when the toy pops off the device it reaches a maximum height of 34 cm
the mass of the toy is 0.65g
the spring is ideal and air resistance and other losses are negligible.
the first part was to work out the constant of the spring,
i used these equations...
Strain potential energy: E = 0.5kx2 and gravitational potential energy: E = mgh
Re-arranging this equation to give k (spring constant) as the subject i get:
K = 2 mgh/ x2
Inserting these values into the equation i get:
K = 2 x(6.5 x 10-4 kg) x 9.81 m s-2 x 0.34 m / (0.012 m)2
giving the value of the spring constant as 30.1 N m
the next part was to work out the magnitude of the force that has to be applied in order to compress the spring sufficiently so the toy can be pressed down to the table.
F = Kx
F = 30.1 kg m2 s-2 x 0.012 m
giving 0.36 N as the answer.
the next part is to calculate the speed in which the toy leaves the table, working on that bit now, hope i'm right so far!!
The energy in the compressed spring is not 0.36N (wrong number, wrong units).To calculate the speed with which the toy leaves the table i will have used the following equation:
E = ½ m v2
Re-arranged to give:
V =√ E / 0.5 x m
V =√ 0.36 N / 0.5 x (6.5 x 10-4)
V = 33.3 m s-1
So the speed is 33.3 m s-1
This seems quite fast!?