Answer:
B
Explanation:
Given that an elevator moving down passes its neighbor, an elevator moving up. Their speed relative to one another is 8 m/s. What is the velocity of each elevator relative to someone standing on the first floor? Assume that the elevators are traveling at the same speed, and that the upward direction is
positive.
Solution
Given that upward direction is positive, then, the downward direction will be negative.
To get a relative velocity of 8m/s
4 - ( - 4 ) = 8
Therefore, the correct answer will be
One elevator is moving at 4 m/s; the other elevator is moving at -4 m/s
Which is option B
Because the negative multiply by negative sign will give positive sign.
Given
4 + 4 = 8.
A sound wave is a longitudinal wave
Answer:
v = 31.3 m / s
Explanation:
The law of the conservation of stable energy that if there are no frictional forces mechanical energy is conserved throughout the point.
Let's look for mechanical energy at two points, the highest where the body is at rest and the lowest where at the bottom of the plane
Highest point
Em₀ = U = m g y
Lowest point
= K = ½ m v²
As there is no friction, mechanical energy is conserved
Em₀ =
m g y = ½ m v²
v = √ 2 g y
Where we can use trigonometry to find and
sin 30 = y / L
y = L sin 30
Let's replace
v = RA (2 g L sin 30)
Let's calculate
v = RA (2 9.8 100.0 sin30)
v = 31.3 m / s