If mass is added to a toy car does it affect its speed making it faster If mass is added to a toy car (29.7g) and dropped down a wooden ramp would it affect its speed making it go faster? I know friction comes in to play to, so if you could give me an answer or an equation to show this that would be. 
 A: Yes, adding mass to a toy car should at least in principle make it accelerate down a ramp faster.
The total force on the car is in the "forward" direction, with magnitude
$$F=m g \sin\theta\ -\ m g C_{rr}\cos\theta\ - \tfrac12 \rho v^2 C_D A\ ,$$
where $m$ is the car's mass, $g$ is the acceleration due to gravity at Earth's surface, $\theta$ is the angle from horizontal of the ramp, $C_{rr}$ is the rolling resistance coefficient, $\rho$ is the density of air, $v$ is the speed of the car, $C_D$ is the drag coefficient of the car, and $A$ is the car's cross section area.  $C_{rr}$ depends on a lot of things rather than being a constant, but what's important here is that for rigid plastic tires, $C_{rr}$ should decrease with increasing $m$.  $C_D$ is independent of $m$.
The first term in the above equation is the forward component of the force purely due to gravity, the second term accounts for rolling resistance, and the third term accounts for drag.   
If you equate that equation with $F=ma$ and divide both sides by $m$, you get that the car's acceleration in the forward direction is
$$a=g \sin\theta\ -\ g C_{rr}\cos\theta\ - \frac{ \rho v^2 C_D A}{2 m}\ .$$
According to that equation, if $m$ increases, so does $a$.
A: If you exclude the forces of air resistance then this becomes the classic "Which falls faster? The baseball, or the cannonball?"
In the case of the cannonball and the baseball, the cannonball will have negligibly more force applied to it, but will accelerate more slowly than the baseball. In the end, they will both hit the ground at the same time.

Big force / Big mass = -9.8m/s$^2$ while Tiny force / Tiny mass also = -9.8m/s$^2$.
A: yes it would, (well if it was moving down a ramp) like you said, friction would also come to play, but it should go faster because the more weight you add the more downwards momentum it gains and if it's moving down a ramp then it should turn that to forward momentum.
