Answer: 686 N
Explanation:
Hi!
Second Newton's law is: F=m*a, where F is force, m is mass, and a acceleration
On the Earth's surface, weight is the gravity force W=m*g, where g=9.8 m/s² is the acceleretion of gravity on Earth. So the weight of someone with mass m=70 kg is W=70*9.8 kg*m/s² = 686 N.
The unit N (Newton) is defined as 1 N = 1 kg*m/s²