Phy Sci 6ed Chap 13 Review

To calculate work done on an object you must mutliply _______ with the magnitude of displacement of the object.

• any force applied to the object

• the force parallel to the object's movment

• the force perpendicular to the object's movement

• the amount of time that the force is applied

Sisyphus pushes his boulder up a hill with a force of 12000 N for 35 s but is unable to move it. How much work is done?

• 0 J

• 420000 J

• 343 J

• 210000 J

A machine with a mechanical advantage _____ will multiply the applied force.

• greater than 1

• less than 1

• equal to 1

• equal to 0

The simple machine of a crowbar being used to pry open a box lid is an example of a

• first-class lever

• second-class lever

• third class lever

• fourth-class lever

Answer explanation

A first-class lever has the fulcrum in the middle

A lever which has the output force in between the input force and the fulcrum

• first-class

• second-class

• third-class

• not a possible lever

the type of lever with the input force (effort) in the middle between the fulcrum and output force (load)

• Pulley
• Second-class lever
• Third-class lever
• First-class lever

Using a first-class lever to pop the lid off a sealed barrel can requires 100 N of input force to be applied downard 1.5 m by your hand to create a 750 N upward output force applied to the lid to move it 0.10 m What is the efficiency of the lever?

• 50%
• 100%
• 75%
• 25%

Answer explanation

efficiency = AMA/IMA

or effieciency = W_out/W_in

AMA = F_out/F_in

IMA = d_in/d_out

W = Fd

what is the IMA of a gear system if your input gear has 64 teeth and the output gear has 36 teeth

• 1.78

• 28

• 0.56

• 2304

Answer explanation

IMA = d_in/d_out

so for a gear system, IMA = (number of input teeth)/(number of output teeth)

An engine hoist is an example of

• gears

• a pulley system/block & tackle

• inclined plane

• a screw

the simle machine shown here has an IMA of

• 2

• 4

• 0.5

• 0.25