Question

A child throws a marble vertically upwards with an initial speed of 98 m/s. Considering the acceleration due to gravity as 9.8 m/s², what is the time taken for the marble to return to its initial position?

A) 10 seconds
B) 20 seconds
C) 14 seconds
D) 0 seconds

Answer 1

The time taken for the marble to return to its initial position is 10 seconds.

Step-by-step explanation:

To find the time taken for the marble to return to its initial position, we can use the kinematic equation:

vf = vi + at

Since the marble is thrown vertically upwards, the final velocity (vf) is 0 m/s when it reaches its highest point. The initial velocity (vi) is 98 m/s in the upward direction. The acceleration (a) due to gravity is -9.8 m/s² (negative because it acts in the opposite direction of upward motion). Plugging in the values:

0 = 98 - 9.8t

Simplifying, we get:

t = 10 seconds

Therefore, the correct answer is A) 10 seconds.