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February 13, 2016

# Homework Help: physics

Posted by Sarah on Monday, June 14, 2010 at 5:08pm.

A spring scale is attached to a cart and is being pulled with a force of 10.5 N. If the car moves to the right with a constant velocity. What are the magnitude and direction of the frictional force?
• physics - MathMate, Tuesday, June 15, 2010 at 8:04am

If the cart moves with a uniform velocity, it means that the forces are in equilibrium (absence of acceleration).
The only vertical forces acting on the cart are its weight (mg) and the normal reaction on the wheel exerted by the floor. Therefore the normal reaction equals mg.

The only horizontal external forces are the spring scale which registers 10.5N and the frictional force.

Can you take it from here?

• physics - Sarah, Tuesday, June 15, 2010 at 10:40am

i do not know what to do from here. this is where I was stuck. what do I do from here.

• physics - MathMate, Tuesday, June 15, 2010 at 8:44pm

There are two horizontal forces, the frictional force F1, and the spring-scale pull (F2), which registers 10.5N.

Since the two are in equilibrium, they have to be equal and opposite. So F1=F2.
What is F1?