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- Summary
- Correct method for Newton's 2nd Law experiment

Hi,

I'm currently having an ongoing debate with some teachers regarding a practical for Newton's Second Law. The prac involves a cart attached to some weights via a string on a pulley. The protocol as it stands has students add increasing mass to the end of the string (not changing the mass of the cart) while measuring the time it takes for the cart to travel a certain distance. The students run the experiment with several different masses and calculate the cart acceleration using time and distance. They then plot the mass at the end of the string against acceleration. The slope is the mass of the cart thus supporting Newton's second Law. I have been arguing that the cart and weight at the end of the string should be used as a total mass and weight should be added to the string by removing it from the cart thus keeping the total mass constant. The calculated mass from the slope is the mass of the entire setup. This has been counter argued that if you had 2 people pulling a car along the road with a rope and you added a third person then you wouldn't take the mass of the people pulling the rope into consideration. Who is right here?

I'm currently having an ongoing debate with some teachers regarding a practical for Newton's Second Law. The prac involves a cart attached to some weights via a string on a pulley. The protocol as it stands has students add increasing mass to the end of the string (not changing the mass of the cart) while measuring the time it takes for the cart to travel a certain distance. The students run the experiment with several different masses and calculate the cart acceleration using time and distance. They then plot the mass at the end of the string against acceleration. The slope is the mass of the cart thus supporting Newton's second Law. I have been arguing that the cart and weight at the end of the string should be used as a total mass and weight should be added to the string by removing it from the cart thus keeping the total mass constant. The calculated mass from the slope is the mass of the entire setup. This has been counter argued that if you had 2 people pulling a car along the road with a rope and you added a third person then you wouldn't take the mass of the people pulling the rope into consideration. Who is right here?