Investigation of Newton’s 2d Law (using virtual air-track)
Print Name _______________________________________Class Period__________
The object of this lab is to investigate how the acceleration of a known mass depends on the force applied to accelerate it.
Theory: According to Newton’s second law of motion, a mass is accelerated in direct proportion to the force acting on it and in inverse proportion to its mass. The law is most commonly written as F = ma . If we plot F vs. a , we should get a straight line whose slope is the mass m.
Materials needed: Virtual Air track, slider cart (wagon), a “massless” pulley and light string, calibrated masses, photo-gate, timer and a graphing program.
Procedure:
1 – From a computer that will run Java, go to the following website: http://www.walter-fendt.de/ph14e/n2law.htm
Here you will find a virtual air track that has a photo-gate (light barrier LB) set at Δx = 0.5 m from the starting point of the slider cart (wagon) so that it will pass the photo-gate and record the time it takes the cart (wagon) to travel from starting at 0 to 0.5 m. The simulator computes and displays the elapsed time and the acceleration of the cart (wagon).
Set the mass of the cart (wagon) at 250 g and the hanging mass at 20 g.
The total mass, M tot
, of the entire combination of the slider cart, mass hanger, string and all the calibrated masses will be M tot
= ____________kg
2 - Click start and let the hanging mass drop. Record the acceleration, computed by the simulator, next to the value of the hanging mass in the table.
3 – Click reset and transfer 10 g from the cart (wagon) to the hanging mass and repeat step 2 above. Do this until the table is complete. (use g = 9.81 m/s
2
)
F = mg hanging mass (kg)
2
) F (N)
.020
.030
.040
.050
.060
.070
4 – Plot F on the Y axis and a on the X axis and make a best fit line.
5 – Compute the slope and use it as the experimentally determined mass. Compare it to the total mass, M tot
, you computed above. Slope _______ % error = _______
1. Turn in a printed copy of this data sheet
2. Turn in a printed copy of your plot (correctly labeled) and
3. Turn in a printed copy of a screen shot of the virtual air track showing at least one the trials you recorded in the table above.