Everything Science Grade 11

12.6 CHAPTER 12. FORCE,MOMENTUM AND IMPULSE

The effort is found by balancing torques.

Fload· rload = Feffort· reffort

980N· 0 .5m = Feffort· 1m

Feffort =

980N· 0 .5m

1m

= 490N

The mechanical advantage is:

mechanical advantage =

load

effort

=

980N

490N

= 2

Since mechanical advantage is a ratio, it does not have any units.

Extension: Pulleys

Pulleys change the direction of a tension forceon a flexible material,e.g. a rope or cable.

In addition, pulleys canbe “added together” tocreate mechanical advantage, by having the

flexible material loopedover several pulleys inturn. More loops andpulleys increases the

mechanical advantage.

Classes of levers ESBFP

Class 1 levers
In a class 1 lever the fulcrum is between the effort and the load. Examples of class 1 levers are the
seesaw, crowbar and equal-arm balance. The mechanical advantage of aclass 1 lever can be increased
by moving the fulcrum closer to the load.

effort

load

fulcrum

Figure 12.19: Class 1 levers

Class 2 levers
In class 2 levers the fulcrum is at the one end of the bar, with the loadcloser to the fulcrum and the
effort on the other endof bar. The mechanicaladvantage of this type of lever can be increasedby
increasing the length ofthe bar. A bottle openeror wheel barrow are examples of class 2 levers.