The image above represents reaction: lift moves down.

To compute for reaction: lift moves down, three essential parameters are needed and these parameters are **mass (m), acceleration (a) **and **acceleration due to gravity (g).**

The formula for calculating reaction: lift moves down:

R = m(g – a)

Where;

R = Reaction

m = Mass

g = acceleration due to gravity

a = Acceleration

Let’s solve an example;

Find the reaction when the mass is 28, acceleration is 9 and acceleration due to gravity is 9.8.

This implies that;

m = Mass = 28

g = acceleration due to gravity = 9.8

a = Acceleration = 9

R = m(g – a)

R = 28(9.8 – 9)

R = 28(0.80)

R = 22.4

Therefore, the **reaction **is **22****.4 N.**

**Calculating the Mass when the Reaction, the Acceleration and the Acceleration due to Gravity is Given.**

m = ^{R} / _{g – a}

Where;

m = Mass

R = Reaction

g = acceleration due to gravity

a = Acceleration

Let’s solve an example;

Find the mass when the reaction is 42, the acceleration is 8 and the acceleration due to gravity is 9.8

This implies that;

R = Reaction = 42

g = acceleration due to gravity = 9.8

a = Acceleration = 8

m = ^{R} / _{g – a}

m = ^{42} / _{9.8 + 8}

m = ^{42} / _{17.8}

m = 2.359

Therefore, the **mass **is **2.359.**