Sarah shoots a toy dart vertically downward at 11.7 m/s at Mark standing on the ground below. Calculate the dart's velocity after 0.8 seconds.

To calculate the dart's velocity after 0.8 seconds, we need to consider two factors: the initial velocity of the dart and the acceleration due to gravity.

The initial velocity of the dart is given as 11.7 m/s downward. Since the dart is moving downward, we can take the initial velocity as negative (-11.7 m/s).

The acceleration due to gravity is a constant value of 9.8 m/s² acting downward.

To find the dart's velocity after 0.8 seconds, we need to use the following kinematic equation:

Vfinal = Vinitial + (acceleration × time)

Plugging in the values we have:

Vfinal = -11.7 m/s + (9.8 m/s² × 0.8 s)
Vfinal = -11.7 m/s + 7.84 m/s
Vfinal = -3.86 m/s

Therefore, the dart's velocity after 0.8 seconds is -3.86 m/s, indicating it is still moving downward but at a slower rate.