Answer:
a) about 20.4 meters high
b) about 4.08 seconds
Explanation:
Part a)
To find the maximum height the ball reaches under the action of gravity (g = 9.8 m/s^2) use the equation that connects change in velocity over time with acceleration.


In our case, the initial velocity of the ball as it leaves the hands of the person is Vi = 20 m/s, while thw final velocity of the ball as it reaches its maximum height is zero (0) m/s. Therefore we can solve for the time it takes the ball to reach the top:

Now we use this time in the expression for the distance covered (final position Xf minus initial position Xi) under acceleration:

Part b) Now we use the expression for distance covered under acceleration to find the time it takes for the ball to leave the person's hand and come back to it (notice that Xf-Xi in this case will be zero - same final and initial position)

To solve for "t" in this quadratic equation, we can factor it out as shown:

Therefore there are two possible solutions when each of the two factors equals zero:
1) t= 0 (which is not representative of our case) , and
2) the expression in parenthesis is zero:

Answer: KE = 25 J
Explanation: You must use the formula
KE = 1/2 m v²
to solve this problem.
KE = 1/2 (10 Kg) (5 m/s)
KE = 1/2 (50 kgm/s)
KE = 25 J
Answer:
Y = Stress / Strain = (F / A) / (l / L) where l is the change in length
Since L is doubled and A remains the same one would expect l, the change in length to also double so Y remains the same.
As an example think of hanging a weight from a spring and the same weight from a similar spring of twice the length - one would expect the longer spring to show twice the extension of the shorter spring.
<span>Water is known as the universal solvent because it is capable of dissolving a variety of substances, more than any other liquid.
Hope this helps!</span>