Help me with two easy physics questions please

Test Preparation
1

<p>Hey guys my physics homework is due on 9/12 and I need help on these two problems.</p>

<li><p>How long is Tina, a ballerina, in the air when she leaps straight up with a speed of 1.8m/s</p></li>
<li><p>A Christmas tree ball will break if dropped on a hardwood floor with a speed of 2.0 m/s or more. Holly is decorating her Christmas tree when her cat Trickor, taps a ball, causing it to fall 15 cm from a tree branch to the floor. Does the ball break?</p></li>
</ol>

<p>I know that there has to be an easy formula for this but I can’t find it. If you can tell me the process by which you get the answer I would be very grateful.</p>

2

<p>I know someone out there knows how to do this. I keep reading about people on this site that get 800's on the SAT II Physics. These questions are really driving me crazy I really really need help.</p>

3

<p>I'm really awful at this, but I'll try:</p>

<p>vi= initial velocity (m/s)
vf= final velocity (m/s)
a= acceleration (m/s^2)
t= time (seconds)</p>

<p>1) For the time going up:
a = (vf-vi)/t
-9.8 = (0 - 1.8)/t
t = 1.8/9.8 = .18, double because she comes down: .367 s</p>

<p>2) d= (vf^2 - vi^2)/2a
.15 = (vf^2 - 0)/2(9.8)
2.94 = vf^2
vf = 1.71 m/s: the ball does not break</p>

<p>Big Five equations rock.</p>

4

<p>a) use the equation v(final) = v(initial) + a<em>t
For the time going up
0 = 1.8 + -9.8</em>t
t=.183
Multiply by two to get total time in the air: .183 * 2 = .367s</p>

<p>tkm is right for the second one</p>

5

<p>Thanks so much! I really suck at Physics so I am sure that there will be a lot of posts from me in the coming year.</p>