Velocity needed to launch a car

[NEUhusky]

Homework Statement

Hi all, this is my first post here because I am having an issue with an assignment in my General Engineering class (physics related). The assignment is to find an action movie clip that portrays something to be real but is, in reality, not possible. My group and I decided on this clip from Transporter 2:



Now, we have three problems in the scene that we need to figure out. We are going to work backwards and start with the velocity a car would need to launch itself off a roof and land on something (we estimated) 18 meters across and 18 meters below. We figured the car dropped about six stories, 10 feet per story, which is approximately 18 meters. We also did some research and found a 4 lane road plus sidewalks would be about 18 meters across. We're allowed to make assumptions as obviously some things cannot be known by just watching a movie.

Homework Equations

I've done multiple kinematics equations but all of the answers seem to be too low. I guess my main question is, how can the mass of the car not be taken into consideration when trying to estimate to the velocity needed for a 4000 pound car to clear 18 meters?

The Attempt at a Solution

There are two unknowns. The initial velocity of the car, and the time it takes for the car to clear 18 meters. My attempt at solving:

-18 = V_iy + (.5)(-9.8)(t²)

=

-18 = -4.9t²

3.67 = t²

t = 1.91 s

Now, knowing the time, I solve for velocity:

18 = V_i(1.91)+(.5)(0)(1.91)

=

18/1.91 = V_i

V_i = 9.42 m/s

9.42 m/s is around 21mph. I'm sitting here looking at my 6 story apartment and trying to visualize a 4000 pound car driving at that slow of pace and landing 18 meters from where it started. What am I missing here? Thanks in advance!(the force needed to break through a concrete barrier will be solved later)

 

[PhanthomJay]

That calc looks good...neglecting air resistance, which should not be too much of a factor in that short time and distance. 20 mph isn't that slow...

 

[NEUhusky]

True. Thanks for the reply. I guess the movie effects are just playing tricks on my eye. The kicker will have to be the force required to break a concrete barrier and sustain the velocity needed to make the jump.