A 21 g bullet is accelerated in a rifle barrel 114 cm long to a speed of 1180 m/s. Use the work-energy theorem to find the avera
1 answer:
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Answer:
The correct option is;
d) Parallel to the plane
Explanation:
The forces acting on the box of mass, m are;
Weight of the box acting an angle, θ, equal to the inclination of the plane to the perpendicular of the plane
Weight of the box acting along the plane = m×g×sin(θ)
The force of friction along the plane = μ×m×g×cos(θ)
The total force acting downward along the plane , = m×g×sin(θ) + μ×m×g×cos(θ)
The Force needed to pull the box up along the plane F = The total force acting downward along the plane
F = m×g×sin(θ) + μ×m×g×cos(θ) = m×g×(sin(θ) + μ×cos(θ))
When the force, Fₐ is applied vertically, the force acting along the plane = Fₐ×cos(θ)
When the force is applied perpendicular, the force acting along the plane = Fₐ×sin(θ)
When the force is applied horizontally, the force acting along the plane = Fₐ×cos(θ)
When the force is applied parallel to the plane, the force acting along the plane = Fₐ
Therefore, since Fₐ > Fₐ×cos(θ) and Fₐ > Fₐ×sin(θ), for acute angles, we have that the least force is required when the force is acting parallel to the plane.
Person standing on A will hear the loudest sound
Explanation:
The intensity of a sound wave (which is proportional to the loudness of the sound) follows an inverse square law, which is:
where
I is the intensity of the wave
r is the distance from the source of the sound
This equation means that the intensity of the sound wave (and therefore, its loudness) is inversely proportional to the square of the distance from the source: therefore,
- As we get closer to the source of sound, the loudness increases
- As we move away from the source of sound, the loudness decreases
Therefore, the person that will hear the loudest sound is the one standing closer to the source, and therefore person A.
Learn more about sound waves:
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