How Does the Weight of a Toy Cart Affect Its Acceleration Going Down a Ramp?

The weight of a toy cart does not affect its acceleration going down a ramp. This counterintuitive fact demonstrates the relationship between gravitational force and mass.

Gravitational force pulls on every particle in an object equally regardless of the object's total mass. As the mass of an object increases, the gravitational force acting upon it proportionally increases. Its inertia also increases, so it requires more force to move the object. Inertia and gravitational force exactly balance out, so gravity on Earth's surface acts with a constant amount of acceleration: 9.8 meters per second squared. How quickly the cart accelerates does, however, depend on the ramp's incline. A steeper ramp allows more gravitational force to move the object and the cart uses less force to push against the solid ramp.

Friction and air resistance also have practical effects. For example, a cart primarily made of a low-density material such as Styrofoam would accelerate more slowly, in Earth's atmosphere, than a cart of the same size primarily made of lead. This is because the Styrofoam must push aside the same amount of air but has less force. A cart with an aerodynamic shape would encounter less turbulence and push aside less air, so it would move more quickly. The shape and size of the cart's wheels also play a part, as rolling objects must overcome rotational inertia to move.