psd2 054 ☈ 14 June 2013 Name:

1. Explain the theory of plate tectonics
2. What is sea floor spreading?
3. What are magnetic pole reversals?
4. __________ _________ Calculate the acceleration of a RipStik that accelerates from 0 cm/s to 204 cm/s in 6 seconds.
5. The time versus distance graph is for a falling ball, how does this graph show that the velocity of the ball is increasing as the drop height increase?
   
6. __________ _________ A ball is dropped a distance d of 100 cm. A timer records a time t of 0.45 seconds. Use this data to calculate the acceleration gravity g.
7. __________ The actual acceleration of gravity g is 979 cm/s². Use the value calculated in the previous problem and calculate the percent error.
8. __________ Plot the data in table one on the graph. Calculate the slope of the line.
   
9. ___________ __________ A 30 kg young girl accelerates from 0 cm/s to 204 cm/s in 6 seconds. How much force was generated in that acceleration?
10. Use the data in table two to answer the following questions on pulleys.

    Table two
    force (gmf)	load (gmf)
    20	50
    80	200
    140	350
    180	450

    1. ____________ Based on the table two data, what is the actual mechanical advantage for the pulley system?
    2. ____________ The pulley system in table two had three load lines. What is the ideal mechanical advantage?
    3. ____________ Use the preceding two questions to calculate the efficiency of the pulley system.
11. What is Newton's first law?
12. What is Newton's third law?

The following questions require some thought and reasoning. The answers are not single word answers. Your answers should be supported by explanations backed up by citing the theories you have explored in class.

13. When a ball is dropped from a height, is the ball half-way down to the ground at half of the time it takes the ball to fall? If the ball is not at half the fall time after falling half the distance, where is the ball - lower or higher? Why? Put another way, if ball takes two seconds to hit the ground, where is the ball at one second? Half way down? Higher? Lower? Why?
14. During a RipStik ride in the classroom I held a ball in the palm of my outstretched hand. I was moving at a constant speed and then I suddenly stopped. The ball kept going. Why did the ball keep going?

$\text{slope m}=\frac{(\mathrm{y2}-\mathrm{y1})}{(\mathrm{x2}-\mathrm{x1})}$
$\text{percent error}=\frac{(\text{experimental value}-\text{expected value})}{\left(\text{expected value}\right)}$
Volume V = length l × width w × height h
mass m = density ρ × Volume V
$\rho =\frac{m}{V}$
distance d = velocity ѵ × time t
$ѵ=\frac{\Delta d}{\Delta t}$
ѵ = at
$a=\frac{\Delta ѵ}{\Delta t}$

d = ½at²
d = ½gt²
$t=\sqrt{\left(\frac{\mathrm{2<mi>d</mi>}}{g}\right)}$
$g=\frac{\mathrm{2<mi>d</mi>}}{t^2}$
Gravitational Potential Energy = mgh
Kinetic Energy = ½mѵ²
momentum = mѵ
Force F = mass m × acceleration a
$\text{efficiency}=\frac{\text{actual mechanical advantage}}{\text{ideal mechanical advantage}}$

where:
a is acceleration
d is distance
Δ is "the change in" (greek lowercase delta)

g is the acceleration of gravity where g is:
g = 980 cm/s² (cgs)
g = 9.8 m/s² (mks)

m is mass
p is momentum
t is time
ѵ is velocity