Answer:
<em>Option b is correct: 4.1 s</em>
Explanation:
<u>Vertical Launch</u>
An object launched thrown vertically upward where air resistance is negligible, reaches its maximum height in a time t, given by the equation:
Where vo is the initial speed and g is the acceleration of gravity g=9.8 .
Once the object reaches that point, it starts a free-fall motion, whose speed is (downward) given by:
The object considered in the question is thrown with vo=25 m/s. The time taken to reach the maximum height is given by [1]:
The object starts its falling motion and at some time, it has a speed of vf=15 m/s. Let's find the time by solving [2] for t:
The total time taken by the object to go up and down is
a. This option is incorrect because it's far away from the answer.
d. This option is incorrect because it's far away from the answer.
b. This option is correct because it's a good approximation to the calculated answer.
e. This option is incorrect because it's far away from the answer.
c. This option is incorrect because it's far away from the answer.