19 - Measuring speeds on a runway When a trolley or toy car moves freely down a slope, it appears to get faster as it nears the bo�om. In this experiment, you will measure the speed of the trolley at different points along an inclined plane by moving the posi�on of the Light gate. An interrupt card fi�ed to the car will break the Light gate’s beam. The so�ware records the �me that the beam is broken by the card. The length of the card is entered in the so�ware, which will then calculate the speed.
Wi r Int eless erf ace
Speed = Distance (length of card) Time (to go through the Light gate)
What you need V-series wireless data logger Light gate Dynamics track, cart and single interrupt card
What you need to do 1.
Assemble the apparatus, construct a catcher for the cart at the end of the track.
2.
Fix the Light gate close to the end of the track, make sure you have enough space a�er the Light gate to let the cart go all the way through. 3. Connect the Light gate to input A on the data logger. 4. Connect the logger to your Bluetooth enabled device. 5. Select Timing from setup and set up the recording to measure speed / velocity at A. You will need to enter the length of the single interrupt card on the cart. 6. Posi�on the cart 10 cm away from the Light gate and click on run. Release the cart, it is best to stop the cart a�er it has gone through the light gate and not rely upon the catcher to stop the cart. 7. The speed will be shown on the graph. 8. Place the cart at the second posi�on on the slope (20 cm from the light gate), and repeat the experiment. 9. Repeat to get speeds from at least 4 distances. Distance from Light gate
Speed / Velocity
Time at A
Ques�ons 1.
Compare the speed values at 10, 20, 30 cm etc. Is there a pa�ern in the way speed changes with distance?
Extensions •
Repeat the experiment with the slope at different heights. Does the shape of the graph change?
•
Does the mass of the trolley or car change the result? Load masses on to the trolley to find out.
Data Harvest Smart wireless ac�vi�es
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