Answer:
1. The velocity of the wagon decreases when Tradi is in the wagon because the mass increases while the external force stays constant.
2. The basic formula for calculating acceleration is a=F/a
Tommy along, acceleration: it will be 2.5 m/s^2. a=100/40
Tommy + Tradi = it will be about 1.66 m/s^2 since a=100/60
3. Well, you see, F=ma, when mass increases, the force decreases.
The relationship between mass and force is inversely proportional.
According to the graphs, velocity increases when there's less mass, which you could say that they are also inversely proportional.
Another comparison,
As the force applied on an object increases, when the mass stays constant, the acceleration also increases. Which means that they are directly proportional.
