A bicyclist 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?

Question

A bicyclist 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?

anonymous · Answer

If she accelerates at 2.1 m/s/s for .3 seconds, then her final velocity is 2.1*0.3 or 0.63 m/s greater than what she started at. If her initial velocity is 5.5 m/s, then her speed after .3 seconds should be 5.5+0.63 or 6.13m/s

anonymous · Answer

the corect answer is 4.87 m/s

anonymous · Answer

Ok, then it was a typo in your original post. She's actually accelerating at negative 2.1m/s/s, so her final velocity is 5.5-.63, or 4.87m/s. That makes more sense

anonymous · Answer

When a driver presses the brake pedal, his car can stop with an acceleration of 5.4 m/s2. How far will the car travel while coming to a complete stop if its initial speed was 25 m/s?
@nolanboat

anonymous · Answer

Ok, do you know that the area under a velocity graph is equal to displacement? If you think about the velocity starting at 25 and decreasing by 5.4 m/s/s, the graph would have the equation $$25-5.4x$$
and you can visualize it in your head as a triangle, but it sort of looks like |dw:1389056987842:dw| because the car comes to a stop after 4.6 seconds.
The area of the triangle is (25*4.6)/2, or 57.875 
So the car traveled 57.875 meters