An airplane can reach a takeoff speed of 45 m/s (from rest) in 7.0 seconds. What is the minimum runway length required for a safe takeoff?

Find acceleration:

acceleration= (final velocity-initial velocity)/time

Then plug into the distance formula:
The distance = (1/2)*(acceleration)*(time)^2 + (initial velocity)*(time)

Is the initial velocity 0?

yes, the key word from the problem: "from rest"

and is the final velocity 45/7?

no, it is the takeoff speed of 45 m/s

To find the minimum runway length required for a safe takeoff, we need to calculate the distance the airplane will travel during takeoff. This can be done using the equation:

Distance = Initial velocity * Time + (1/2) * Acceleration * Time^2

In this case, the initial velocity is 0 m/s (since the airplane starts from rest), the time is 7.0 seconds, and we need to find the acceleration.

The acceleration can be calculated using the equation:

Acceleration = (Final velocity - Initial velocity) / Time

In this case, the final velocity is the takeoff speed of 45 m/s, the initial velocity is 0 m/s, and the time is 7.0 seconds.

Plugging these values into the equation, we get:

Acceleration = (45 m/s - 0 m/s) / 7.0 s = 6.43 m/s^2

Now we can substitute the values into the distance equation:

Distance = 0 m/s * 7.0 s + (1/2) * 6.43 m/s^2 * (7.0 s)^2

Calculating this equation, we find:

Distance ≈ 150.02 meters

So the minimum runway length required for a safe takeoff is approximately 150.02 meters.