physics help

Test Preparation AP Test Preparation
1

<p>Hey guys...
This is probably not AP physics level but can you help me on these questions anyway with the work shown please?</p>

<ol>
<li><p>When air resistance on a falling skydiver builds up to 0.3 the weight of the skydiver, what is the acceleration of the skydiver?</p></li>
<li><p>On the moon, the acceleration due to gravity is 1/6 that on Earth. What would be the weight of 0.9 kg of bologna on the moon?</p></li>
<li><p>On the surface of Jupiter, the acceleration due to gravity is about 3 times that on Earth. How much would a 0.40-kg rock weigh on Jupiter?</p></li>
<li><p>A certain unbalanced force gives a 20-kg object an acceleration of 2.0m/s2. What acceleration would the same force give a 30-kg object?</p></li>
<li><p>You push with 10.0 N on a 5.0-kg block and there are no opposing forces. How fast will the block accelerate?</p></li>
<li><p>A 400,000-kg airplane in takeoff uses the 40,000 N thrust of each one of its four engines. What is the acceleration of the plane during takeoff?</p></li>
</ol>

<p>I did some of these problems but I wasn't sure on some of them....If you can do only a few that would be great too...
Thanks!! :)</p>

2

<ol>
<li><p>W = mg
F = .3W - W = ma
F = .3mg - mg = ma
F = -.7mg = ma
F = -.7g = a
a = -6.86 m/s^2</p></li>
<li><p>g<em>moon = (1/6)g</em>earth
W = mg
W = .9 * (1/6)g_earth
W = .9 * (1/6)9.8
W = 1.47 N</p></li>
<li><p>g<em>jupiter = 3g</em>earth
W = mg
W = .4 * 3g_earth
W = .4 * 3 * 9.8
W = 11.76 N</p></li>
<li><p>F = ma
ma of 20-kg object will equal ma of 30-kg object since the forces are equal
20 * 2 = 30 * a
a = (4/3) m/s^2</p></li>
<li><p>F = ma
a = F/m
a = 10/5
a = 2 m/s^2</p></li>
<li><p>F = ma
40,000 * 4 = 160,000 N (since there are four engines)
a = F/m
a = 160000 / 400,000
a = .4 m/s^2</p></li>
</ol>

3

<p>thank you so much~~ :)</p>

4

<p>im sry to ask you again but can u see if i did the following two problems correctly?</p>

<ol>
<li><p>A net force of 1.0 N acts on a 4.0-kg object, initially at rest, for 4.0 seconds. What is the distance the object moves during that time?
Answer: 2m</p></li>
<li><p>How much (in newtons) does a 10.0-kg bag of grass seed weigh?
Answer: 98N</p></li>
</ol>

<p>Thanks again!</p>

5

<p>Yes and yes.</p>