Question

Formula:

Answer 1

Acceleration is the rate of change of velocity

when velocity increases its acceleration

and when the velocity decreases its called decelaration

the formula to calculate acceleration is as follows

$a = \frac{v-u}{t}$

where

a - acceleration

v - final velocity

u - initial velocity

t - time taken

1. airplane starting at rest means initial velocity - 0 m/s

final velocity - 80 m/s

time - 20 s

substituting the values in the equation

a = (80 m/s - 0 m/s) / 20 s = 80 / 20 = 4 m/s²

the acceleration is 4 m/s² north

2. cyclist starts at rest so initial velocity - 0 m/s

time - 20 s

acceleration - 0.5 m/s²

substituting values in the equation

0.5 m/s² = (v - 0 m/s)/ 20 s

0.5 = v / 20 s

v = 0.5 x 20 = 10 m/s

final velocity is 10 m/s south

Answer 2

According to the formula you have given us to work with . . .

1). The airplane's acceleration is

(80 m/s north - zero) / (20 sec) = 4 m/sec^2 north

2).  For the cyclist:

                                          (V-final - zero) / 20sec = 0.5 m/s^2 south

Multiply each side by 20s :  V-final = 0.5 m/s^2 south x (20sec) = 

                                                                                         10 m/s south