Arturo O. answered 11/03/16
Experienced Physics Teacher for Physics Tutoring
Fn = normal force = ?
m = 0.518 kg
g = 9.81 m/s2
T = 5.23 N
θ = 51.0° (I am assuming this angle is above the horizontal, which is not stated in the problem.)
Set up equilibrium of forces in the vertical direction.
Tsinθ + Fn = mg
Fn = mg - Tsinθ
Fn = (0.518 kg)(9.81 m/s2) - (5.23 N)sin(51.0°) ≅ 1.02 N