A car travelling at 72km/h drives off a cliff 400m high.
How long does it take to hit the ground?
9 sec
To find out how long it takes for the car to hit the ground, we can use the laws of motion and the equation of motion known as the kinematic equation for distance.
The kinematic equation for distance is given by:
s = ut + (1/2)at^2
Where:
s = distance
u = initial velocity
t = time
a = acceleration due to gravity
In this case, we need to find the time (t) it takes for the car to hit the ground. We know that the initial velocity (u) is 0 m/s because the car is not moving horizontally when it falls off the cliff. The acceleration (a) due to gravity is approximately 9.8 m/s^2, directed downward.
We are given that the car falls from a height of 400 meters. Therefore, the distance (s) is 400m.
Plugging in the known values into the equation, we have:
400 = 0*t + (1/2)(9.8)*t^2
Simplifying the equation:
400 = 4.9t^2
Dividing through by 4.9, we have:
t^2 = 400 / 4.9
t^2 ≈ 81.63
Taking the square root of both sides to isolate t, we get:
t ≈ √81.63
t ≈ 9.04 seconds
Therefore, it will take approximately 9.04 seconds for the car to hit the ground.