Answer: 0.5 seconds or 2.625 seconds
Explanation:
At t = 0, The ball is 4 ft above the ground.
The height of the football varies with time in the following way:
s(t) = -16 t² + 50 t + 4
we need to find the time in which the height would of the football would be 25 ft:
⇒25 = -16 t² + 50 t + 4
we need to solve the quadratic equation:
⇒ 16 t² - 50 t + 21 = 0
⇒ t = 0.5 s or 2.625 s
Therefore, at t = 0.5 s or 2.625 s, the football would be 25 ft above the ground.
Answer:
1. Running velocity (5 m/s)
2. Resting velocity (0 m/s)
3. Walking velocity (-1 m/s)
1. Running speed (5 m/s)
2. Walking speed (1 m/s)
3. Resting speed (0 m/s)
Explanation:
Attached you will find the plot of position vs time of Ellie´s movement.
The velocity is the displacement of the object over time relative to the system of reference. The speed, in change, is the traveled distance over time in disregard of the system of reference.
So, the velocity is calculated as follows:
v = Δx / Δt
where
Δx = final position - initial position
Δt = elapsed time
1) The average velocity of Ellie while running is:
v = 1000 m - 0 m / 200 s = 5 m/s
While resting:
v = 0 m - 0 m / 100 s = 0 m/s
And while walking back:
v = 0 m - 1000 m / 1000 s = - 1 m/s
Note that in this last case, the initial position is 1000 m because Ellie is 1000 m from the origin of the system of reference when she walks back. The final position will be the origin of the system of reference, 0 m.
Comparing with the graphic, the velocity is the slope of the function position(t).
Then:
1. Running velocity (5 m/s)
2. Resting velocity (0 m/s)
3. Walking velocity (-1 m/s)
2) The speed is the distance traveled over time:
Running speed = 1000 m / 200 s = 5m /s
Resting speed = 0 m / 100 s = 0 m/s
Walking speed = 1000 m/ 1000 s = 1 m/s
Then:
1. Running speed (5 m/s)
2. Walking speed (1 m/s)
3. Resting speed (0 m/s)
