Abicyclist is moving at a speed of 5.5 m/s. she squeezes the brakes, giving her an acceleration of -2.1 m/s². how fast is the bicyclist going after 0.3 seconds of applying the brakes?

Formula relating time, velocity and acceleration:

Vf = Vi + at (Vf = Final velocity, Vi = initial velocity)

What you're given:
Initial speed, Vi = 5.5 m/s
Acceleration, a = -2.1 m/s^2
Time, t = 0.3 s

Required:
Vf = ?

Plugging in the given information:

Vf = (5.5) + (-2.1)(0.3)
Vf = 4.87 m/s

The bicyclist's speed is 4.87 m/s after 0.3 s.

That depends on what kind of environ meant it is in  in space it has the same force that was applied when the velocity was gained

What the heck r u talkin bout? ?