Harnessing the sun's energy to produce heat or electricity is : A. Non - Polluting
This energy generating method will cause no dangerous emission for environment (unlike the one that came from fossil fuel), but the energy that produced from the sun tend to be more expensive so it's still not widely used
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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:
C. Decreasing the distance between the objects.
Explanation:
Gravitational force depends on mass and distance. The farther the objects are apart, the less gravitational force/pull they have.
Answer:
They are the only joints that can do 360 degrees and rotate with their own axis. But, because of its free-moving, it is prone to any dislocation compared to other movable joints.
Explanation:
The statement is true because an object will remain not moving until an external force is applied into. so in order to move an object external force should be applied. for example an object fell down, even no one pushes it pulls it, but the force due to gravity is acting on it so there is still a force acting on it.
