Question:
A 63.0 kg sprinter starts a race with an acceleration of 4.20m/s square. What is the net external force on him? If the sprinter from the previous problem accelerates at that rate for 20m, and then maintains that velocity for the remainder for the 100-m dash, what will be his time for the race?
Answer:
Time for the race will be t = 9.26 s
Explanation:
Given data:
As the sprinter starts the race so initial velocity = v₁ = 0
Distance = s₁ = 20 m
Acceleration = a = 4.20 ms⁻²
Distance = s₂ = 100 m
We first need to find the final velocity (v₂) of sprinter at the end of the first 20 meters.
Using 3rd equation of motion
(v₂)² - (v₁)² = 2as₁ = 2(4.2)(20)
v₂ = 12.96 ms⁻¹
Time for 20 m distance = t₁ = (v₂ - v ₁)/a
t₁ = 12.96/4.2 = 3.09 s
He ran the rest of the race at this velocity (12.96 m/s). Since has had already covered 20 meters, he has to cover 80 meters more to complete the 100 meter dash. So the time required to cover the 80 meters will be
Time for 100 m distance = t₂ = s₂/v₂
t₂ = 80/12.96 = 6.17 s
Total time = T = t₁ + t₂ = 3.09 + 6.17 = 9.26 s
T = 9.26 s
When you are talking about the Principle of mechanical Energy Conservation, it is really only including the kinetic and potential energy in a total system. When frictional forces are present, although the conservation of energy law is still present, it does not work when it comes to the conservation of mechanical energy as there is another type of energy that is factored in. As friction acts on the object, that transition from potential to kinetic as it slide/falls will be completely different as some of that energy is being transformed into thermal energy. Which breaks the conservation of mechanical energy.
Solar Energy is the answer to the question tell me if i`m wrong
<span>Winds can greatly affect the amount of precipitation an area receives depending on the amount of moisture they are carrying. These prevailing winds can move air masses from the ocean onto a continent bringing moisture onto the continent. ... Prevailing winds affect the climate of an area.
(From Google)</span>
The June solstice in the Northern hemisphere is the summer solstice. The June Solstice in the Southern hemisphere is the winter solstice. The summer solstice is equivalent to the longest day while the winter solstice is equivalent to the shortest day. Therefore on the local sky, when is the June solstice we have have the longest day (longest path of sun in the sky) in the Northern hemisphere and the shortest day (shortest path of sun in the sky) in the Southern hemisphere.
