Average speed of the car is defined as the ratio of total distance and total time
So here we will have
now we know that
time = 5 h
now from above equation we will have
so the average speed will be 90 km/h
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.
