<em>number of waves that pass a given point in one second is called <u>frequency..</u></em>
Answer:
This is due to a relative decrease in atmospheric pressure in high places.
Explanation:
Given that atmospheric pressure decreases at the higher point or ground, this reduced atmospheric pressure, however, will be unable to contain the Mercury in the barometer tube.
Therefore, at the top of the mountain where the air pressure is low, the barometer reading ultimately goes down.
Hence, the level of mercury falls in a barometer while taking it to a mountain "due to a relative decrease in atmospheric pressure in high places."
You want to draw a free body diagram of the forces on the sled in the horizontal x-direction.
If you visualize the system in an x-y coordinate plane, the force along the x-direction is the angle it makes with the x-axis multiples by the force.
The angle made with the x-axis is cosine of the angle theta.
Please see picture attached.