Answer
given,
cooling fan revolution = 850 rev/min
fan turns before revolution = 1500 revolutions


θ = 1500 revolution
θ = 1500 x 2 x π
θ = 9424.78 rad
a) using equation of rotation
ω² = ω₀² + 2 α θ
ω = 0 because body comes to rest
0 = 89² + 2 x α x 9424.78
α = -0.42 rad/s²
b) time take for the fan to stop
ω = ω₀ + α t
0 = 89 - 0.42 t

t = 211.9 s
Answer:
Mass of the cart = 146 kg
Explanation:
A cart is pulled by a force of 250 N at an angle of 35° above the horizontal.
The cart accelerates at 1.4 m/s² horizontally.
Horizontal force = Fcosθ = 250 cos35° = 204.79N
We have F = ma
Substituting
204.79 = m x 1.4
m = 146.28 kg = 146 kg
Mass of the cart = 146 kg
Neutrons don't have any charge
It takes sunlight 8 minutes to reach earth , so yes