# How much force needed to push a car on neutral? [closed]

The car is a 2002 Toyota Corolla SE I have in my garage on a stone surface, I.e., the floor itself.

What I want to know is how to determine the force needed to get it in motion at all.

The curb weight is 2,400 lbs. How could I determine the force needed to push it on neutral to get it in any kind of motion?

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The biggest factor is probably all the internal friction in the vehicle (without friction it would require no force at all), and as such not answerable by us. –  Chris White Jul 13 at 3:06
I don't understand what friction you aelre referring to –  legate stroke Jul 13 at 3:07
@ChrisWhite but you don't think it should be closed? –  David Z Jul 13 at 3:16
@DavidZaslavsky well, I figured maybe there was a chance there was an easy non-engineering solution ::shrug:: legate stroke: any surfaces in contact and moving relative to one another lose energy to friction. All the moving parts in the car contribute, and without this effect, you could push a car with your little finger if you so chose. –  Chris White Jul 13 at 3:20
@Chris I dunno, I think if you have to italicize "maybe" then that's not really enough to justify leaving it open ;-) I mean, if you really think the question is a good one and appropriate to remain open, by all means, don't VTC, but it seems to me like this falls under the engineering category, or insufficient prior research. –  David Z Jul 13 at 3:25

## closed as off-topic by Chris White, Dan, Dilaton, David Z♦Jul 13 at 8:07

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "This question appears to be about engineering, which is the application of scientific knowledge to construct a solution to solve a specific problem. As such, it is off topic for this site, which deals with the science, whether theoretical or experimental, of how the natural world works. For more information, see this meta post." – Chris White, Dan, Dilaton, David Z
If this question can be reworded to fit the rules in the help center, please edit the question.

You may have come across the terms static friction and dynamic friction. In brief, the force needed to get an object moving is generally less that the force needed to keep it moving. Cars show this phenomenon, though for different reasons to the usual lab experiments of sliding blocks around. Car bearings are designed to maintain a thin film of oil when they're moving, but when the car is stationary this film collapses and the friction rises considerably. The point of this is that Maxim's idea wouldn't give you a good idea of the force needed to get the car going, though it would give you the dynamic friction.

This is one way of doing it:

Drive the car onto a platform of length $d$, then release the handbrake and put it into neutral. Now start jacking up one end of the board, and measure the height $h$ at which the car just starts to roll. (You might want someone in the car to stop it! :-)

If the mass of the car is $m$, then the force propelling the car forward is $F = mg\sin\theta$, where $\theta$ is the angle the board makes to the floor. The value of $\sin\theta$ is given by:

$$\sin\theta = \frac{h}{\sqrt{h^2 + d^2}} \approx \frac{h}{d}$$

where the approximation is good if $h \ll d$.

So the force required to start the car moving is:

$$F = mg \left( \frac{h}{\sqrt{h^2 + d^2}} \right)$$

By just measuring the distances $h$ and $d$ you can calculate what force you'll need to start the car moving.

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You seem to have not finished your point or explanation. –  legate stroke Jul 13 at 18:56
@legatestroke: I've edited my reply to give the final formula for calculating the force –  John Rennie Jul 14 at 6:52
Giving me that formula is very pointless; I have no idea on how to use it. –  legate stroke Jul 15 at 3:10