John was riding his bike at 15m/s. He braked to stop at an intersection. It took him 5 seconds to come to a stop. What was his acceleration?
To find John's acceleration, we can use the equation:
acceleration = (final velocity - initial velocity) / time
In this case, John's initial velocity is 15 m/s (riding his bike) and his final velocity is 0 m/s (stopped at the intersection). The time it took him to stop is 5 seconds. By substituting these values into the equation, we can find the acceleration:
acceleration = (0 m/s - 15 m/s) / 5 s
acceleration = -15 m/s / 5 s
acceleration = -3 m/s²
Therefore, John's acceleration is -3 m/s². The negative sign indicates that his acceleration is in the opposite direction of his initial velocity, which means he is decelerating or slowing down.