When there is a stunt car and it goes up a ramp, why does it fly over a gap and onto another ramp, without falling down the hole in the middle? What is the physics behind it? What does kinetic energy and momentum and acceleration have to do with it?
Lets think about how the car is moving as it leaves the
end of the first ramp. It is travelling at high speed at an angle to the ground with its trajectory
slightly upwards.
You can think of this motion as being split into two directions – one
horizontal and one vertical. The horizontal one does not change (if we ignore the air
resistance) but the vertical one gets less as the car is pulled down by gravity.
As
long as the gap is not too big and the speed of the car is big enough it will have crossed the
gap before the gravitational attraction has pulled it down to the level of the second
ramp.
In a way it is just like a long jumper. The athlete launches themselves
upwards at the take off board and if they are also travelling fast down the runway they will
travel a long way before they hit the ground again. Long jumpers must give themselves this
upwards push as well as sprinting fast if they are to achieve large distances.
If you
would like some actual numbers concerning the car:
(It all depend on how much maths
and theoretical physics you have covered as to whether you will understand al of
this)
Imagine that the car is moving at 20 m/s at an angle of 10 degrees to the
horizontal when it leaves the ramp.
Using the equation for a projectile [Range =
u2 sin(2A)/g] it will describe a parabolic path in the air and reach the level of the
second ramp after travelling a horizontal distance of 13.9 m.
If the speed is
increased to 30 m/s and the angle to 20 degrees then:
Using the equation for a projectile
[Range = u2 sin(2A)/g] it will describe a parabolic path in the air and reach the
level of the second ramp after travelling a horizontal distance of 59 m!
Obviously air
resistance will cut down both these distances quite a bit!
