# Lab Calculations that will be on the Unit Test

• Waterballoon Slingshot lab summary of calculations:

1.  Started with a time for a vertical launch. ½ of this time is how long it was going up, half of this time is how long it was coming down.

2.  Using half of the time, and the acceleration due to gravity, find the initial vertical velocity (which is equal to the magnitude of the velocity when it reaches the ground.)

Useful Formula:   vf=vi+at

3.  You have just found the launch velocity.  If the balloon is shot at an angle, the initial velocity will still be this velocity.   However, it can be resolved into a horizontal component and a vertical component.

Draw a right triangle with your angle & find these components.

Useful formulas:  Ax=Acos(angle)     Ay=Asin(angle)

4.  The vertical component of this launch velocity is what controls how long it will be in the air.   Since you’re not shooting it straight up, it won’t be in the air for as long as the original time.   To find the new time in the air, it’s just like the first two steps above, going backwards.

Useful Formula:   vf=vi+at

Use this formula to find the time.

5.  Then, multiply this time by 2 because it’s only the amount of time for it to go up, or for it to come down.

6.  Now, you have a total time that it’s in the air.   You also have the horizontal component of its velocity.   Find how far horizontally the balloon travels.

Useful Formula:   d=vt

Ball Rolling off the desk classroom activity:

1.  Use the height of the desk to determine how much time the ball will be in the air.

Useful Formula: d=vit+ ½ at2           Initial velocity = 0m/s

2.  Find the horizontal velocity of the ball just as it leaves the edge of the table.  (The horizontal velocity will not change while the ball is in the air.)

3.  Find the distance away from the desk that the ball lands by  using  d=vt

Softball Toss Lab:

1.  Use the time in the air to determine the initial vertical velocity.   Divide the time by two (because it’s going up for half of the time and down for half of the time.    On the way down, the initial vertical velocity is zero.  Find the final vertical velocity using:   vf=vi+at

2.  The horizontal velocity is constant.  (It doesn’t accelerate in the horizontal direction.)   Find the horizontal velocity by using how far it went horizontally divided by the total time it was in the air.

d=v/t

3.   Draw a right triangle.   Find the angle using the tangent function.   Find the resultant by using the Pythagorean theorem.

4.  Note:  You may also have to draw the triangle to scale & find the angle using a protractor & calculate the initial velocity by measuring the length of the hypotenuse and using the scale.