Chapter 4, Problem 15RQ

How many forces are exerted on the horse-cart system? What is the net fore on the horse-cart system?

To determine

The number of forces exerted on the horse-cart system and the net force on the horse system.

Answer to Problem 15RQ

The force $P$ applied by the horse reaction force $F$ by ground applied to the horse and force of friction $f$ acting on the cart wheels. And the net horizontal force on the horse is $F-f$.

Explanation of Solution

The free body diagram of the horse-cart system is shown below,

In the horse and cart system, force $P$ applied by the horse and reaction $P$ exerted by the cart are internal forces that cancel out each other. In a whole horse-cart system, it is subjected to two external forces, reaction force $F$ by ground applied to the horse and force of friction $f$ acting on the cart wheels.

The reaction force $F$ and force of friction $f$ acts in opposite direction. Hence net force acting on the horse-cart will be equal to difference of $F-f$.

Write the expression for net horizontal force act on the horse.

$F_{system}=F-f$

Here,

$f$ is the friction force

$F$ is the reaction force

Conclusion:

Therefore, the force $P$ applied by the horse reaction force $F$ by ground applied to the horse and force of friction $f$ acting on the cart wheels. And the net horizontal force on the horse is $F-f$.