What Are the Key Variables in Projectile Motion on Planet Exidor?

[Jeff231]

Homework Statement

A physics student on PLanet Exidor throws a ball, and it follows hte parabolic trajectgory shown in the figure. The ball's position is shown at 1.00 intervals until t=3.00. At t=1.00, the ball's velocity is v=(2.00i + 2.00j)[m/s].

a. Determine the ball's velocity at t=0, 2.00, and 3.00.
b. What is the value of g on the Planet Exidor?
c. What was the ball's launch angle?

Homework Equations

<br /> v = v_0 + a t<br /> &lt;br /&gt; &lt;br /&gt; &amp;lt;br /&amp;gt; x = x_0 + v_0 t + (1/2) a t^2&amp;lt;br /&amp;gt; &amp;amp;lt;br /&amp;amp;gt; &amp;amp;amp;lt;br /&amp;amp;amp;gt; v^2 = v_0^2 + 2 a \Delta x&amp;amp;amp;lt;br /&amp;amp;amp;gt; &amp;amp;amp;amp;lt;br /&amp;amp;amp;amp;gt; &amp;amp;amp;amp;lt;br /&amp;amp;amp;amp;gt; &amp;amp;amp;amp;lt;br /&amp;amp;amp;amp;gt; &amp;amp;amp;amp;lt;br /&amp;amp;amp;amp;gt; &amp;amp;amp;amp;lt;h2&amp;amp;amp;amp;gt;The Attempt at a Solution&amp;amp;amp;amp;lt;/h2&amp;amp;amp;amp;gt;&amp;amp;amp;amp;lt;br /&amp;amp;amp;amp;gt; &amp;amp;amp;amp;lt;br /&amp;amp;amp;amp;gt; I was able to find at 1.00&amp;amp;amp;amp;lt;s&amp;amp;amp;amp;gt; that the ball&amp;amp;amp;amp;amp;#039;s acceleration in the x direction = 2.00[m/s^2]. I&amp;amp;amp;amp;amp;#039;m not really sure how to find the velocity at t=0 &amp;amp;amp;amp;lt;s&amp;amp;amp;amp;gt; since I think it can&amp;amp;amp;amp;amp;#039;t be zero. I&amp;amp;amp;amp;amp;#039;m pretty if I can figure out the max height I can figure out what g is. But I can&amp;amp;amp;amp;amp;#039;t find max height. &amp;amp;amp;amp;lt;br /&amp;amp;amp;amp;gt; &amp;amp;amp;amp;lt;br /&amp;amp;amp;amp;gt; Thanks.&amp;amp;amp;amp;lt;br /&amp;amp;amp;amp;gt; &amp;amp;amp;amp;lt;/s&amp;amp;amp;amp;gt;&amp;amp;amp;amp;lt;/s&amp;amp;amp;amp;gt;

 

[Kurdt]

With all projectile motion problems you need to consider both components of motion. There should be no acceleration in the x direction. At the top of the parabola what do you expect the y component of velocity to be? This will help you with what you know about t = 1 to set up some simultaneous equations and solve the problem.

 

[loonychune]

There should be no acceleration in the x direction.

It will really help to rewrite

<br /> v = v_0 + at = v_0 - gt<br />

where I've defined g downwards as positive as two equations then...

<br /> v_x = ... \quad \&amp; \quad v_y = v_y(t)=...<br />

 

[Jeff231]

Thanks for the help. It was stupid of me to think of ax instead of just thinking g the whole time. This clarified things a bunch, thanks!