Question

A bridge that was 5.0 m long has been washed out by the rain several days ago. How fast must a car be going to successfully jump the stream? Although the road is level on both sides of the bridge, the road on the far side is 2.0 m lower than the road on this side.

Answer 1

The speed of the car is 7.84 m/s

Solution:

As per the question:

Length of the bridge, l = 5.0 m

Distance, d = 2 m

Now,

Time taken by the car to reach 2 m lower is given by the kinematic eqn:

`d = ut + (1)/(2)at^(2)`

where

u = initial velocity = 0 m/s

t = time taken

a = g =
`9.8\ m/s^{}`

Now,

`2 = 0.t + (1)/(2)* 9.8* t^(2)`

`t = 0.638\ s`

Now, we kow that the car will cover the distance equal to the length of the bridge, i.e., 5 m

Speed of the car is given by:

`v = (distance\ covered)/(time\ taken)`

`v = (5.0)/(0.638) = 7.84\ m/s`