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Answer: B. store electric charges.
Explanation: I JUST TOOK THE PF EXAM AND I GOT IT CORRECT!!!!
Answer:
a. 16 s b. -1.866 kJ
Explanation:
a. Since the initial rotational speed ω₀= 3313 rev/min = 3313/60 × 2π rad/s = 346.94 rad/s. Its rotational speed becomes ω₁ = 0.75ω₀ in time t = 4 s.
We find it rotational acceleration using α = (ω₁ - ω₀)/t = (0.75ω₀ - ω₀)/t = ω₀(0.75 - 1)/t = -0.25ω₀/t = (-0.25 × 346.94 rad/s)/4 s = -21.68 rad/s².
Since the turntable stops at ω = 0, the time it takes to stop is gotten from
ω = ω₀ + αt and t = (ω - ω₀)/α = (0 - 346.94 rad/s)/-21.68 rad/s² = (-346.94/-21.68) s = 16 s.
So it takes the turntable 16 s to stop.
b. The workdone by the turntable to stop W equals its rotational kinetic energy change.
So, W = 1/2Iω² - 1/2Iω₀² = 1/2 × 0.031 kgm² × 0² - 1/2 × 0.031 kgm² × (346.94 rad/s)² = 0 - 1865.7 J = -1865.7 J = -1.8657 kJ ≅ -1.866 kJ
Answer:
The answer to your question is: a = 1.99 m/s²
Explanation:
Data
mass = 20 kg
angle = 56°
Force = 71 N
horizontal acceleration = ?
Process
Find the horizontal force
cos Ф = adjacent side / hypotenuse
adjacent side = hypotenuse x cosФ
adjacent side = 71 x cos 56
a.s. = 39.70 N
Newton's second law
F = ma
a = F/m
a = 39.7 / 20
a = 1.99 m/s²
The target heart rate for moderate-intensity activity is 80%