A 10000 N car comes to a bridge during a storm and finds the bridge washed out.
ID: 1326803 • Letter: A
Question
A 10000 N car comes to a bridge during a storm and finds the bridge washed out. The 700 N driver must get to the other side, so he decides to try leaping it with his car. The side the car is on is 22.0 m above the river, while the opposite side is a mere 4.00 m above the river. The river itself is a raging torrent 63.0 m wide.
How fast should the car be traveling just as it leaves the cliff in order to clear the river and land safely on the opposite side?
What is the speed of the car just before it lands safely on the other side?
Explanation / Answer
Car has to fall through a vertical distance of 22-4 = 18 m . During this time, it must cross the bridge.
Let us 1st calculate time taken to fall.
use:
h = 0.5*g*t^2
18 = 0.5 * 9.8* t^2
t = 1.92 s
To cross 63 m, its speed must be greater than : d/t = 63/1.92 = 32.9 m/s
Minimum speed of car should be travelling at 32.9 m/s
When it falls by 18 m, vertical speed gained,
Vy = g*t = 9.8*1.92 = 18.82 m/s
Horizontal velocity remains same which is 32.9 m/s
Total speed before landing = sqrt (32.9^2 + 18.82^2) = 37.9 m/s
Speed of car before it lands = 37.9 m/s
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