Target Lab
Purpose: You will use your understanding of freefall and horizontal motion to predict where a projectile will land.
Procedure:
1. You will roll a steel ball down an inclined track. Because of gravity, the ball will accelerate.
2. First you will focus on the vertical portion of the ball’s motion. Measure the height of the end of the
track off the floor. This is how far the ball will be falling.
3. Calculate the time that it will take for the ball to reach the ground, using this formula: (remember than g
is the acceleration of gravity and is 10 m/s2).
𝑡=√
2𝑑
𝑔
4. Record the time in your data table.
5. Next focus on the horizontal portion. At the bottom, the track becomes horizontal, so the speed of the
ball becomes constant. You will measure the speed of the ball at this point, using an infrared photogate.
a. Make sure that the timer is turned on and set to interval. Make sure that the A light is on.
b. Roll the ball from the top of the track. Record the time from the photogate on your data table.
c. Divide the diameter of the ball by the photogate time. This will give you the horizontal speed (vx)
of the ball. Record this in your data table.
6. You know that the ball’s horizontal speed will remain constant. Since you know the speed and the time
that it is in the air, you can now determine how far the ball will travel horizontally using the following
equation:
v
d
t
Now you will use this information to predict the landing spot of the ball. You will place your soup cup on that
exact spot. Roll the ball down the track. You get only one shot at this, and it MUST be done in front of Mr.
Mower or Ms. McKenna. If the ball lands in the cup, you will receive extra credit.
DATA TABLE
Photogate time:
Ball diameter:
Height of track:
0.019m
Horizontal velocity: (ball diameter divided by photogate
time)
Time to fall:
Distance traveled:
Target Lab
1.
Was your prediction accurate? Did the ball land in the cup?
2.
If not, what error(s) do you think may have caused you to miss? (Be specific; do not just say “human
error”)
3.
Would the ball have taken the same amount of time to reach the ground if it was not moving
horizontally (i.e., if you simply dropped it from that height)? Explain.
4.
Why doesn’t the ball change velocity in the horizontal axis?