If a girl is standing still and holding a box, is she doing any work? Why or why not?
2 answers:
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Define an x-y coordinate system such that
The positive x-axis = the eastern direction, with unit vector
.
The positive y-axis = the northern direction, with unit vector
.
The airplane flies at 340 km/h at 12° east of north. Its velocity vector is
The wind blows at 40 km/h in the direction 34° south of east. Its velocity vector is
![\vec{v}_{2} =40(cos(34^{o})\hat{i} - sin(24^{o})]\hat{j}) = 33.1615\hat{i} -22.3677\hat{j})](https://tex.z-dn.net/?f=%5Cvec%7Bv%7D_%7B2%7D%20%3D40%28cos%2834%5E%7Bo%7D%29%5Chat%7Bi%7D%20-%20sin%2824%5E%7Bo%7D%29%5D%5Chat%7Bj%7D%29%20%3D%2033.1615%5Chat%7Bi%7D%20-22.3677%5Chat%7Bj%7D%29)
The plane's actual velocity is the vector sum of the two velocities. It is
The magnitude of the actual velocity is
v = √(121.1615² + 306.0473²) = 329.158 km/h
The angle that the velocity makes north of east is
tan⁻¹ (306.04733/121.1615) = 21.6°
Answer:
The actual velocity is 329.2 km/h at 21.6° north of east.
The positive x-axis = the eastern direction, with unit vector
The positive y-axis = the northern direction, with unit vector
The airplane flies at 340 km/h at 12° east of north. Its velocity vector is
The wind blows at 40 km/h in the direction 34° south of east. Its velocity vector is
The plane's actual velocity is the vector sum of the two velocities. It is
The magnitude of the actual velocity is
v = √(121.1615² + 306.0473²) = 329.158 km/h
The angle that the velocity makes north of east is
tan⁻¹ (306.04733/121.1615) = 21.6°
Answer:
The actual velocity is 329.2 km/h at 21.6° north of east.
The car will slow down due to the negative acceleration (backward)
Explanation:
The figure is missing: find it in attachment.
To answer this question, we have to use Newton's second law, which states that:
where
F is the net force on an object
m is its mass
a is its acceleration
We have to apply this law separately on the horizontal direction and vertical direction.
- In the vertical direction, we have two forces acting on the car: 2000 N upward and 2000 N downward, so they cancel out, and the net force in the vertical direction is zero.
- In the horizontal direction, the net force is instead
In the backward direction (to the right).
So, according to Newton's second law, the car will experience a horizontal acceleration:
And the acceleration has the same direction as the net force (so, backward). This means that the acceleration is opposite to the direction of motion of the car, so the car will slow down, since its velocity will decrease.
Learn more about acceleration:
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