Final answer:
To calculate the braking force to slow down an 80 kg bike and rider from 5 m/s to a stop in 2 seconds, use Newton's second law and find an acceleration of -2.5 m/s², leading to a force of -200 N.
Step-by-step explanation:
The student is asking about the braking force required to slow a combined mass of a person and a bicycle, which is 80 kg, from a speed of 5 m/s to a stop in 2 seconds. To find the braking force, we can use Newton's second law, F = ma, where F is the force, m is the mass, and a is the acceleration. First, we need to calculate the acceleration using the formula a = Δv / t, where Δv is the change in velocity and t is the time taken for the change. In this case, Δv is -5 m/s (since the final velocity is 0 and the initial velocity is 5 m/s, the change is 5 m/s subtracted from 0 m/s), and t is 2 seconds, yielding an acceleration of -2.5 m/s². The negative sign indicates deceleration. Then, we apply the force equation F = ma with m = 80 kg and a = -2.5 m/s² to find the braking force.
The braking force F is calculated as F = ma = 80 kg × (-2.5 m/s²) = -200 N. The negative sign indicates the force is in the opposite direction to the motion, which makes sense since it's a braking force.