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:

The answer to this is Helium :) it's in the farthest right columb and is a noble gas.
please mark as brainliest!
Answer: For 18 the inch is longer im not sure by how much, for 19 the the kilogram is 2.2 times heavier than a pound, QUART IS A LITTLE LESS THAN A LITER. ... An easy way to figure from liters to gallons, for example, is that a quart is a little less than a liter and 4 liters is a little more than 1 gallon. To be exact, 1 liter is 0.264 gallon (a little more than a quart), and 4 liters is 1.06 gallons, 30°C or 30°F? Correct answer: the table shows that 30°C is about 86°F, which is warmer than 30°F. And sorry Im not sure how to do the rest
Explanation: