Answer:
θ = 73.6º
Step-by-step explanation:
To solve this exercise, let's use Newton's second law. Let's set a reference system where the x-axis is parallel to the inclined plane
with trigonometry we can find the components of the weight
sin θ = Wₓ / W
cos θ= W_y / W
Wₓ = W sin θ
W_ = W cos θ
Y axis
N - W_y = 0
N = W_y
X axis
Wₓ - fr = m a
mg cos θ - fr = m a
indicate that friction is zero, fr = 0
cos θ = a / g
θ = cos⁻¹
let's calculate
θ = cos⁻¹
θ = 73.6º