Calculating Friction Force: A Toy Train Example

[dance_sg]

Homework Statement

A toy train moves along the track at 9.0m/s. When the power is turned off, the train comes to a stop in 6.0s. The net force on friction acting on the train to stop it is

Homework Equations

F=ma

The Attempt at a Solution

how do i find mass and acceleration so that i can find force??

 

[Doc Al]

Enough information is given for you to figure out the acceleration using kinematics, but not enough to find the friction force. Are you sure you are presenting it word-for-word as it was given?

 

[dance_sg]

yes I am one hundred percent sure.

 

[kuruman]

yes I am one hundred percent sure.

This bothers me. Consider a real life freight train moving at the same initial speed and stopping in the same time. Surely the average force acting on it must be greater in this case. Something is missing or the problem cannot be done the way it is phrased.

 

[RoyalCat]

This bothers me. Consider a real life freight train moving at the same initial speed and stopping in the same time. Surely the average force acting on it must be greater in this case. Something is missing or the problem cannot be done the way it is phrased.

Yes, the scaling factor is the mass of the freight train compared to that of the toy train. Their accelerations would be the same, but as their masses are different, the force required to bring about those accelerations would differ.

As for my perspective on the problem, I could single out the coefficient of kinetic friction, but couldn't for the life of me find an expression for the mass in terms of the question's data, so the actual force eluded me.

 

[Doc Al]

Something is missing or the problem cannot be done the way it is phrased.

Right. As I said, there is not enough information given to solve for the net force.