Post by: :) on October 27, 2009, 06:04:37 pm
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 :)
Post by: /0 on October 27, 2009, 06:16:05 pm
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.
Post by: NE2000 on October 27, 2009, 07:30:20 pm
Post by: Hooligan on October 28, 2009, 03:08:33 pm
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