How do you find the answer, I know it's simple, but I'm missing it!
A horizontal force is used to pull a 5.0 kg cart at a constant speed of 5.0 m/s across the floor. If the force of friction between the cart and the floor is 10.0N, the the horizontal force on the handle of the cart is.....?
Here what we need to recognise is the first law of Newton.
His first law of motion says that an object will be at rest or travelling in constant velocity until an external force applied on it. so in this stage the net force on an object is zero.
The cart is travelling at a constant speed. So the net force on the cart should be zero according to the first law of Newton.
There are two forces acting on the cart. One is the horizontal force that pulls the cart and the other is the friction acting against the motion. Since the net force is zero the force that pulls the cart should be equal to the friction force.
So the force that pulls the cart is 10N.
here if the cart is moving in constant speed in a horizontal path then by newton's first law the net force on it should be zero.
thus only the force required to overcome friction is applied externally.
thus the external horizontal force is 10.0N