Weight (W) = Mass (m) × Acceleration due to gravity (g)

Here's the breakdown:

* Mass (m): 100 kg (given)

* Acceleration due to gravity (g): Approximately 9.8 m/s² (standard value on Earth)

Therefore:

* Weight (W) = 100 kg × 9.8 m/s² = 980 N

So, the force of weight of a 100kg man in gravity is approximately 980 Newtons.