Understanding the Concepts

* Work: Work is done when a force causes an object to move a certain distance. It's calculated as: Work (W) = Force (F) x Distance (d)

* Force due to Gravity: The force acting on an object due to gravity is its weight, calculated as: Force (F) = Mass (m) x Acceleration due to gravity (g). The acceleration due to gravity (g) is approximately 9.8 m/s².

Calculations

1. Calculate the force due to gravity:

* F = m * g

* F = 21 kg * 9.8 m/s²

* F = 205.8 N (Newtons)

2. Calculate the work done:

* W = F * d

* W = 205.8 N * 7 m

* W = 1440.6 J (Joules)

Answer: The work done to lift the object is 1440.6 Joules.