This is a power problem which requires the rearranging of a formula. The lamps energy used is 5 N, and the TV’s usage is 116.7 N (rounded from 116.6666repeating). Here my work:
Gravity Gravitational Force of Gravity
Answer: 
Explanation:
Given
Intensity must be reduced by a factor of 6
Intensity is given by 
Substitute
by 

So, the disk must be rotated by an angle of
.
Answer:
2 s, -20 m/s
Explanation:
Given:
y₀ = 20 m
y = 0 m
v₀ = 0 m/s
a = -9.8 m/s²
Find: t and v
y = y₀ + v₀ t + ½ at²
0 = 20 + 0 + ½ (-9.8) t²
0 = 20 − 4.9 t²
t ≈ 2 s
v² = v₀² + 2a(y − y₀)
v² = 0 + 2(-9.8)(0 − 20)
v ≈ ±20 m/s
Since the rock is falling, v = -20 m/s.
Answer : The acceleration of the elevator is, 
Explanation :
Formula used to calculate the acceleration of the elevator is:

where,
F = force = 844 M
m = mass of man = 70 kg
g = acceleration due to gravity = 
a = acceleration of the elevator = ?
Now put all the given values in the above formula, we get:



Thus, the acceleration of the elevator is, 