Final answer:
Using the kinematic equation for vertical motion, the ball thrown up with an initial velocity of 20 m/s will reach a maximum height of roughly 20.4 m. The closest answer to this calculated height is option B. 21 m.
The correct answer is B.
Step-by-step explanation:
Calculating the Maximum Height Reached by a Ball:
To calculate the maximum height reached by a ball thrown straight up with an initial velocity, we can use the following kinematic equation for vertical motion under constant acceleration (gravity):
[h = v^2/(2g)], where:
- h is the maximum height,
- v is the initial velocity,
- g is the acceleration due to gravity (approximately 9.81 m/s^2).
Let's consider the ball with an initial velocity of 20 m/s:
[h = (20 m/s)^2 / (2 × 9.81 m/s^2)]
After the calculation:
h = 20.4 m
This value indicates that the maximum height the ball will reach is 20.4 m. Hence, the correct answer among the provided options is B. 21 m, by approximation.