One
Without any consideration other than the givens the acceleration will be 2 m/s^2
Givens
F = 100 N
m = 50 kg
a = ?
Formula
F = m*a
Solution
100 N = 50 kg * a Divide both sides by 50
100 N/50 kg = 50 kg * a / 50 kg
2 m/s^2 = a
Two
The (downward) gravitational force is
Givens
F = m * a
m = 50 kg
a = 9.8 m/s^2
Solution
F = 50 * 9.8
F = 490 N