Solution to problems – class 9 – Set 1 Q 29

Problem Statement

A plane has a takeoff speed of 100 m/s and requires 1500 m to reach that speed. Determine the acceleration of the plane and the time required to reach this speed.

Solution

It starts from rest. So initial velocity U = 0 

Final velocity = take off velocity = V = 100 m/s 
 
To acquire that final velocity the distance travelled = S= 1500 m

To find out the acceleration, we will use the equation
V² = U² + 2 a S

As U = 0, the equation becomes: V² = 2 a S

Which gives acceleration
a = V² / (2 S)
= 100 ² / (2×1500) = 3.3 m/s²

To find out the time required to reach that speed we will use this equation V=U + at

As U =0, the equation becomes V = at

which gives the time as:   t = V/a = 100/3.3 = 30.3 sec

Question Set – Physics Problems for grade 9