Final answer:
An 84 kg astronaut exerts a force of 823.44 N on his chair while at rest on the launch pad, calculated using the weight formula W = m × g.
Step-by-step explanation:
The force an 84 kg astronaut exerts on his chair while sitting at rest on the launch pad is equivalent to his weight. The weight of an object on Earth can be found by using the equation W = m × g, where W is the weight, m is the mass, and g is the acceleration due to gravity (approximately 9.81 m/s² on Earth).
Therefore, the astronaut's weight, and thus the force exerted on the chair, is 84 kg × 9.81 m/s², which equals 823.44 N (newtons).