Hooke's Law

Today in physics we reviewed what we did on Friday which was total energy and how the amount of kinetic energy and the amount of potential energy are always equal to the starting total energy.

We then moved on to look a springs, more specifically, Hooke's Law which contains stuff about the spring constant and how far from equilibrium the sping is depressed or stretched.

Ex: A compressed spring that obeys Hooke's law has a potential energy of 18 J. If the spring constant is 400 N/m, find the distance by which the spring is compressed.

Ep = 18 J

k = 400N/m

x = ?

Ep=1/2kx^2

=to find x we manipulate the formula to get the root of 2ep/k

= the root of 36/400

=3/10 or .30m the spring compressed.

We also looked at finding the total energy and the maximum height of an object, in this case, a golf ball.

Ex: Determind the total mechanical enerygy of a 48g golf ball if it has a velocity of 25 m/s when it leaves the club face.

m = .048 kg

vi = 25 m/s

hi = 0 m

et = 1/2mv^2

=1/2(.048)(25^2)

=15J

b) If the golf ball goes in an arc and has a speed of 15 m/s at its maximum height, what will the maximum height be?

h = ?

Et = 15 J

m = .048 kg

v = 15m/s

Et=mgh+1/2mv^2

15J=(.048kg)(9.8m/s^2)(h)+1/2(.048)(15^2)

And to find h we manipulate the formula and eventually get that the height is 20m.

Landon is next.