Answer:
640 J
Explanation:
ΔKE = KE − KE₀
ΔKE = ½ mv² − ½ mv₀²
ΔKE = ½ m (v² − v₀²)
ΔKE = ½ (80 kg) ((5 m/s)² − (3 m/s)²)
ΔKE = 640 J
Her kinetic energy increases by 640 J, so she does 640 J of work.
He is describing the motorcycle's acceleration. <span />
The smallest size of the insect that the bats can detect corresponds to the wavelength of the chirp they emit.
Their chirp has a frequency of

and the speed of the chirp is equal to the speed of sound in air:

Therefore the wavelength of the chirp is

which corresponds to a size of 4.76 mm.
Correct free-body diagram is option A)
Explanation:
There are three forces acting on Patricia:
- Her weight, which is the force of gravitational attraction exerted by the Earth on her, whose magnitude is
(where m= mass and g= acceleration of gravity). The direction of this force is vertically downward. - The normal force, exerted by the plane on Patricia, which acts always up perpendicular to the plane
- The force of friction, which prevents Patricia from sliding. The force of static friction acts in the direction opposite to the direction of motion if the body is let moving: so here, the force of friction acts up along the plane (parallel to the plane)
Therefore, the correct choice here is option A), because:
- The weight acts vertically downward
- The normal force acts perpendicular to the plane
- The force of friction acts parallel to the plane
Learn more about forces:
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