Pushing / Pulling force

[:)]

What's the difference between a pushing force and a pulling force?

For example question 9 TSSM 2009:
An object of mass M kg is PUSHED along a rough horizontal surface by a force F1 inclined alpha degrees to the horizontal, where 0 < alpha < pi/2. Another object of the same mass M kg is pulled along the same surfae by a force F2 with the same inclination of alpha degrees to the horizontal.  Both objects are moving with constant velocity.

a) Show that the force F1 has a greater magnitude than the force F2

Thanks

[/0]

If we assume that F1 is pushing down and F2 is pulling up, then F1 > F2.

If F1 is pushing down then the normal force is increased, so the retarding frictional force will be increased. If F2 is pulling up then the normal force is decreased, so the retarding frictional force is decreased. Therefore you require F1 > F2 for the object to move at constant velocity.

[NE2000]

As /0 said, it's all to do with friction. Try drawing a diagram, it will make it clearer.

[Hooligan]

What's the difference between a pushing force and a pulling force?

For example question 9 TSSM 2009:
An object of mass M kg is PUSHED along a rough horizontal surface by a force F1 inclined alpha degrees to the horizontal, where 0 < alpha < pi/2. Another object of the same mass M kg is pulled along the same surfae by a force F2 with the same inclination of alpha degrees to the horizontal.  Both objects are moving with constant velocity.

a) Show that the force F1 has a greater magnitude than the force F2

Thanks

Have a look at the solutions. They've drawn the diagrams in there, where you can clearly see that the pushing force affects the vertical component, differently to that of the pulling force.

In the pushing case, you would have whereas with the pulling force, you would have .