Mechanical Advantage and the Inclined Plane: More Practice

Mechanical Advantage and the Inclined Plane: More Practice

Mechanical Advantage and the Inclined Plane: More Practice

Mechanical Advantage and the Inclined Plane: More Practice

Mechanical Advantage and the Inclined Plane: More Practice

Levers and Torque: Student Learning GoalThe student will be able to solve problems

involving torque, force, load-arm length, and effort-arm length as they relate to levers (C2.5).

Levers and Torque

SPH4C

The Lever

A lever is a rigid bar that can rotate freely around a support called a fulcrum.

Torque

When a force causes a rigid body to rotate, we say that a torque has been applied.

Torque is defined as the turning effect.

Torque

Torque (T) increases as force (F) increases and also increases as distance (d) from the fulcrum increases:

Torque

Torque (T) increases as force (F) increases and also increases as distance (d) from the fulcrum increases:

FdT

Torque

Torque (T) increases as force (F) increases and also increases as distance (d) from the fulcrum increases:

Torque has units of N m.

FdT

Torque: Example

A force of 84 N is used to turn a wrench of length 25 cm. What was the torque on the wrench?

Torque: Example

A force of 84 N is used to turn a wrench of length 25 cm. What was the torque on the wrench?

Torque: Example

A force of 84 N is used to turn a wrench of length 25 cm. What was the torque on the wrench?

?:

25.025

84:

TUnknown

mcmd

NFGivens

Torque: Example

A force of 84 N is used to turn a wrench of length 25 cm. What was the torque on the wrench?

?:

25.025

84:

TUnknown

mcmd

NFGivens

Torque: Example

A force of 84 N is used to turn a wrench of length 25 cm. What was the torque on the wrench?

?:

25.025

84:

TUnknown

mcmd

NFGivens

mNmNTSolve

FdTSelect

21)25.0)(84(:

:

Load torque and Effort torqueFor any lever there are two torques: the load

torque (TL) and the effort torque (TE):

EEE

LLL

dFT

dFT

dL and dE are referred to as the load arm and effort arm, respectively.

Static Equilibrium

If the load torque equals the effort torque, the lever is in static equilibrium.

Static Equilibrium

If the load torque equals the effort torque, the lever is in static equilibrium.

EL TT

EELL dFdF

Static Equilibrium: ExampleWhat force does your bicep need to exert to hold a

weight of 134 N (30 lbs)?

Remember that the human forearm is a lever.

Static Equilibrium: ExampleWhat force does your bicep need to exert to hold a

weight of 134 N (30 lbs)?We will ignore the weight of the forearm itself.

?

:

05.05

3.030

134

:

E

E

L

L

F

Unknown

mcmd

mcmd

NF

Givens

Static Equilibrium: ExampleWhat force does your bicep need to exert to hold a

weight of 134 N (30 lbs)?

?

:

05.05

3.030

134

:

E

E

L

L

F

Unknown

mcmd

mcmd

NF

Givens

Static Equilibrium: ExampleWhat force does your bicep need to exert to hold a

weight of 134 N (30 lbs)?

?

:

05.05

3.030

134

:

E

E

L

L

F

Unknown

mcmd

mcmd

NF

Givens

N

m

mNFSolve

Fd

dFdFdFSelect

E

EE

LLEELL

80405.0

3.0134:

:

Or approximately 800 N

More Practice

Levers and Torque Lab Activity