Education and Manpower Bureau
Using Datalogger in the Teaching of Physics

Pushing and Pulling a Dynamics Cart

Experiment Profile:

1. Background

Newton's Second Law describes: The acceleration of an object is directly proportional and in the same direction as the net force on the object but inversely proportional to the mass of the object. The experiment will investigate this relationship by pushing and pulling a dynamics cart back-and-forth on a level track using data-logging equipment.

2. Objective

 Investigate the relationship of the force exerted on a cart, the mass of the cart and the acceleration of the cart as it moves.

3. Equipment List

 Datalogger interface connected to a PC Dynamics cart Motion sensor Force sensor bracket & bumpers Newton force sensor Air track Balance (to measure mass)

 Experiment Collision and Conservation of Momentum Simple Harmonic Motion Acceleration due to Gravity Pushing and Pulling a Dynamics Cart Acceleration of a Dynamic Cart

 Procedure.

 1 Connect the datalogger interface to a PC with the software installed. 2 Connect the motion sensor and force sensor to the interface. 3 Place the air track on a horizontal surface and fix the motion sensor to one end of the track. 4 Place the force sensor on top of the dynamics cart. 5 Place the cart on the air track with the hook of the force sensor pointing away from the motion sensor. 6 Before recording the data, ensure that the force sensor is reset at zero. 7 Start the data-logging software and start recording the data. 8 Hold the hook of the force sensor and pull and push the force sensor to make the cart move back and forth. Please note the minimum distance for the Motion sensor and make sure the cart does not come too close to the motion sensor. 9 Push and pull the cart back and forth four or five times, then stop recording the data.

Analysis:

 1 Measure and record the mass of the cart plus the force sensor. 2 From the collected data, plot a force versus acceleration curve for the cart as it moves back and forth in front of the motion sensor. 3 Find the slope of the curve. The slope of the curve is the mass of the cart plus the force sensor. 4 Is the value of the slope from the graph equal to the mass of the cart you measured? If yes, Why? 5 If there is any difference, try to explain the reason.

 Acknowledgements We are particularly grateful to Carmel Pak U Secondary School for their help in the production of this video.

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