- #1

DarkEnergy890

- 14

- 3

- Homework Statement
- A cyclist exerts a constant force of 450 N causing the bicycle to accelerate at 4.8 m s-2

until reaches a velocity of 20 m s-1 due west. Given that the combined mass of the

cyclist plus the bicycle is 120 kg, calculate (i) the net force (ii) the frictional force.

- Relevant Equations
- F=ma

My understanding is that the Net Force = Force Applied + Frictional Force. The net force is F=ma, so net force = 576N. Now 576N=450N + Frictional force, so frictional force has to be 126N.

My confusion is this:

1. Force is a vector, and the frictional force opposes the direction of motion. Therefore shouldn't friction turn out to be a negative?

2. If the applied force is 450N, then how can the net force be 576N, more than the force applied? If anything, I think that friction should cause the net force to be less than the applied force.

Here is the marking scheme (model answer) : https://prnt.sc/tyhQTEm0WKAw

Thanks!

My confusion is this:

1. Force is a vector, and the frictional force opposes the direction of motion. Therefore shouldn't friction turn out to be a negative?

2. If the applied force is 450N, then how can the net force be 576N, more than the force applied? If anything, I think that friction should cause the net force to be less than the applied force.

Here is the marking scheme (model answer) : https://prnt.sc/tyhQTEm0WKAw

Thanks!