Find the net force (in Newtons)

[tica86]

Find the net force (in Newtons) required to accelerate a 110 kg bike and rider from rest to a final velocity of 22.7 m/s in 10 seconds?

since f=ma 110(22.7)=2497 do I divide that by 10 seconds??

 

[cepheid]

No. Think about it. If you tried what you are suggesting, your result would have dimensions of [force]/[time], which is not physically meaningful here. You're looking for a force. To get the force, you need to know the acceleration so that you can apply Newton's second law, as you correctly stated. However, you made a mistake. You substituted the velocity (22.7 m/s) in for the acceleration. Velocity is not acceleration -- they are two very different things! I hope you understand how they differ.

In this problem, the acceleration is an unknown. To find it, you will need to consider the kinematics of the problem. ;)

 

[tica86]

No. Think about it. If you tried what you are suggesting, your result would have dimensions of [force]/[time], which is not physically meaningful here. You're looking for a force. To get the force, you need to know the acceleration so that you can apply Newton's second law, as you correctly stated. However, you made a mistake. You substituted the velocity (22.7 m/s) in for the acceleration. Velocity is not acceleration -- they are two very different things! I hope you understand how they differ.

In this problem, the acceleration is an unknown. To find it, you will need to consider the kinematics of the problem. ;)

Thanks for pointing that out. So to find acceleration a=v2-v1/10s
I get a=22.7-0/10=2.27?

 

[cepheid]

Yeah that looks right to me, provided you assume the acceleration is constant. Acceleration = (change in velocity) / (change in time).

 

[tica86]

Yeah that looks right to me, provided you assume the acceleration is constant. Acceleration = (change in velocity) / (change in time).

So the final answer would be
ma=110(2.27)=249.7N?