In the Newton's 2nd Law experiment, a cart and added mass was connected by a string to a hanging mass. When released it accelerated down a track. The hanging mass W2 was increased by moving mass from the cart to the hanging mass. The accumulated data was then plotted as W2 vs. acceleration. A best fit straight line was drawn to the data.
What does the slope of this line represent?
A) the mass of the cart
B) the force of friction
C) the hanging mass
D) the total mass of the system.

Question

In the Newton's 2nd Law experiment, a cart and added mass was connected by a string to a hanging mass. When released it accelerated down a track. The hanging mass W2 was increased by moving mass from the cart to the hanging mass. The accumulated data was then plotted as W2 vs. acceleration. A best fit straight line was drawn to the data. 
What does the slope of this line represent? 
A) the mass of the cart  
B) the force of friction 
C) the hanging mass
D) the total mass of the system.