Gross Out
A hill to climb
You're on your way for a cold beer when your ambulance gets stuck in a gully - can you escape like they did in Ice Cold In Alex?
Over-egged?
Urine - and then you're out?
Related programme
If the bus took off from a flat surface and tried to land on another flat surface the same height, as it appears to in the film, it would not have been possible. The bus would have fallen 2.27m and crashed into the raised freeway. Nasty!
Bus with no ramp:
To clear the 50ft gap on the freeway, what is needed is a jump (an angled surface) So why is this and what angle is required? If we take an angle of, say, 30 degrees, then travelling at 75mph the bus will start with an initial upwards velocity (speed in certain direction). What would the upwards (vertical) and horizontal velocities be?
Bus with ramp:
If the bus is taking off (literally) at a 30 degree angle, at 75mph, then there will be a motion upwards (vertical) and a motion forwards (horizontal). These motions are independent of each other, which means you can split them up and work out how far the bus travels, upwards/downwards and forwards/backwards.
This is done using good old trigonometry.
So for the vertical motion the speed at which the bus is going upwards initially is:
The bus would decrease in speed upwards due to gravity, until it stops and then start falling, like throwing a ball upwards. How long would the bus take to rise and fall to the same level?
Final speed = initial speed + (acceleration x time)
1.675 seconds to reach the top of its flight.
How high has the bus gone, before it starts to comes down?
Average speed = (initial speed + final speed)/2 for a constant acceleration.
Therefore:
The height climbed in 1.675 seconds is then:
8.375 x 1.675 =14m.
To fall 14m due to gravity will take how long? Another 1.67 seconds. So the total time will be approximately 3.3 seconds.
That’s how long you have to make the jump, but is this enough? Can the bus move forwards 50ft in 3.3 seconds? What is the horizontal velocity?
Therefore in 3.3 seconds the bus would travel
29 x 3.3 = 95.7m (314ft).
No problem: the bus would fly over the hole. We can see the effect of the angle on time and length of jump in this table.
| Time | Angle (degrees) | Horizontal speed (mph | Vertical speed upwards at take off (mph) | Time that the bus is in the air in seconds | Distance of jump in ft | Does the bus make it? |
| 50 | 2 | 50 | 1.7 | 0.16 | 25.4 | crash |
| 50 | 5 | 49.8 | 4.3 | 0.39 | 63.1 | boom |
| 50 | 10 | 49.2 | 8.6 | 0.76 | 122.8 | boom |
| 60 | 2 | 60 | 2.1 | 0.19 | 36.8 | crash |
| 60 | 5 | 59.8 | 5.2 | 0.46 | 90.8 | clear |
| 70 | 2 | 70 | 2.4 | 0.22 | 49.8 | crash |
| 70 | 5 | 69.7 | 6.1 | 0.54 | 123.6 | clear |
| 80 | 2 | 80 | 2.8 | 0.25 | 65 | clear |
| 80 | 5 | 79.7 | 6.9 | 0.62 | 121.4 | clear |
| 90 | 1 | 90 | 1.6 | 0.14 | 41.2 | crash |
| 90 | 2 | 89.9 | 3.1 | 0.28 | 82.3 | clear |
We haven’t accounted for deceleration due to wind resistance, which is a variable, and could greatly reduce the distance jumped.
Next time you are racing along in a bus trying to prevent a bomb blowing up, take your eyes off Keanu Reeves/Sandra Bullock. If you want to know if you can scale that gap in the road, get out your calculator!
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