Answer:
a. 1222.13 J b. 2.36 m. His new position is above his original position
Explanation:
From work-kinetic energy principle, workdone = change in kinetic energy
So work the skateboarder does on himself W₁ = -116 J
work done by friction W₂ = -264 J
gravitational potential energy change W₃ = mgΔy
The kinetic energy change ΔK = 1/2m(v² - u²) where m = mass of skater = 52.9 kg, u = initial speed of skaterboarder = 2.04 m/s and v = final speed of skaterboarder = 6 m/s. ΔK = 1/2m(v² - u²) = ΔK = 1/2 × 52.9(6² - 2.4²) = 842.13 J
So, W₁ + W₂ + W₃ = ΔK
W₃ = ΔK - W₁ - W₂ = 842.13 J - (-116 J) - (-264J) = 842.13 J + 116 J + 264J = 1222.13 J
b. Since W₃ = mgΔy = 1222.13 J
Δy = W₃/mg = 1222.13/(52.9 × 9.8) = 1222.13/518.42 = 2.36 m
Since Δy > 0, his new position is above his original position.
Answer:
soil additive
Explanation:
Soil Additive
The three main components of humus are fulvic acid, humic acid and humin. The spongy nature of humus helps it to trap and hold water, this particular property also helps to aerate the soil as humus expands and contracts with available water.
B. A wave travels through medium. Hope this helped!
Answer:
25 km/h
Explanation:
speed=distance÷time
125÷5=speed
125÷5=25 (then add units)
Answer:
h = 78.4 m
Explanation:
Given that,
A stone takes 4s for the stone to touch the river's water surface.
We need to find the height of the bridge from the water level.
Let the height be h. We can use the second equation of motion to find h. So,
![h=ut+\dfrac{1}{2}gt^2\\\\ \because u=0\\\\So,\\\\h=\dfrac{1}{2}\times 9.8\times 4^2\\\\h=78.4\ m](https://tex.z-dn.net/?f=h%3Dut%2B%5Cdfrac%7B1%7D%7B2%7Dgt%5E2%5C%5C%5C%5C%20%5Cbecause%20u%3D0%5C%5C%5C%5CSo%2C%5C%5C%5C%5Ch%3D%5Cdfrac%7B1%7D%7B2%7D%5Ctimes%209.8%5Ctimes%204%5E2%5C%5C%5C%5Ch%3D78.4%5C%20m)
So, the height of the bridge from the water level is 78.4 m.