First, Second, and Third Class Levers Quiz & Flashcards

Questions and Answers

What is a lever?

A lever is a beam on a fulcrum.

Where is the force transmitted?

The force is transmitted across a length around another point.

What is the benefit of a lever?

The benefit of a lever is that less force is required to move an object with more mass.

What are the three types of levers?

First class, second class, and third class. Signup and view all the answers

Describe a first class lever.

The axis is between the force and the resistance arm, and the force arm may be greater than, smaller than, or equal to the resistance arm. Signup and view all the answers

Where is the fulcrum in a first class lever?

The fulcrum is between the input and output force meaning it is in the middle. Signup and view all the answers

Give an application of a first class lever.

A first class lever is shown in a scissor or a crowbar. Signup and view all the answers

Describe a second class lever.

The resistance lies between the effort force and the axis of rotation, and the force arm is greater than the resistance arm. Signup and view all the answers

Where is the fulcrum in a second class lever?

In a second class lever the fulcrum is at the end, with the load in the middle. Signup and view all the answers

Give an application of a second class lever.

One application of a second class lever is a wheel barrel. Signup and view all the answers

Describe a third class lever.

The effort force lies closer to the axis of the lever than the resistance, and the force arm is smaller than the resistance arm. Signup and view all the answers

Where is the fulcrum in a third class lever?

In a third class lever the fulcrum is again at the end, but the effort is in the middle. Signup and view all the answers

Give an application of a third class lever.

One major application of a third class lever is that they are in cranes. Signup and view all the answers

What is torque?

The ability of a force to cause rotation around an axis. Signup and view all the answers

What is another name for torque?

Moment of force. Signup and view all the answers

What is the formula for torque?

T = F x d Signup and view all the answers

What are the names of the variables used in the formula for torque?

T (torque) = F (force) x d (distance) Signup and view all the answers

What are the units used in torque?

For metric units use Newtons, for American units inch-pounds. Signup and view all the answers

Mechanic pulls on a 6-inch wrench with a force of 100 lbs. What is the torque?

T = 600 in-lbs. Signup and view all the answers

What is mechanical advantage?

The ratio of the output force to the input force. Signup and view all the answers

What is the formula for mechanical advantage?

MA = LE (Effort Length) / LR (Resistance Length) Signup and view all the answers

Which class lever has little to no mechanical advantage?

Third class lever have 0.25 mechanical advantage. Signup and view all the answers

Define the Law of Moments.

The effort force equals or greater than the resistance moment then the lever is in rotational equilibrium. Signup and view all the answers

What is the formula for the Law of Moments?

FE x LE = FR x LR and ME has to be greater than or less than MR. Signup and view all the answers

Define each variable in the Law of Moments.

FE = Effort Force, LE = Effort Length, FR = Resistance Force, LR = Resistance Length, ME = Effort Moment, MR = Resistance Moment. Signup and view all the answers

Study Notes

Levers Overview

A lever consists of a beam supported by a fulcrum to transmit force across a length around a pivot point.
Levers require less force to move heavier objects, enhancing mechanical efficiency.

Types of Levers

There are three classes of levers: first class, second class, and third class.

First Class Lever

The fulcrum is positioned between the effort force and the resistance, allowing flexibility in force distances.
Common examples include scissors and crowbars.

Second Class Lever

The resistance force is located between the effort force and the fulcrum, which is at one end.
A notable application is the wheelbarrow, where effort applied makes lifting easier.

Third Class Lever

The effort force is positioned between the fulcrum and the resistance force, generally leading to less mechanical advantage.
Cranes exemplify this class, requiring greater input force for the output achieved.

Torque

Torque represents the tendency of a force to cause rotation around an axis, also known as the moment of force.
The formula for torque is T = F x d, where T is torque, F is force, and d is the distance from the fulcrum to the point of application.

Mechanical Advantage

Mechanical advantage (MA) measures the effectiveness of the lever, defined as the ratio of output force to input force.
Its formula is MA = LE / LR, where LE is effort length and LR is resistance length.
First class levers can have mechanical advantages of up to 2, while third class levers typically have a mechanical advantage of about 0.25.

Law of Moments

The Law of Moments states that for a lever to be in rotational equilibrium, the effort moment must equal or exceed the resistance moment.
The formula is FE x LE = FR x LR, where FE is effort force, LE is effort length, FR is resistance force, and LR is resistance length.

Variables for Law of Moments

FE: Effort Force
LE: Effort Length
FR: Resistance Force
LR: Resistance Length
ME: Effort Moment
MR: Resistance Moment

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Description

Test your knowledge about the fundamental principles of levers with this quiz. Explore definitions, benefits, and the different types of levers. Perfect for students seeking to understand simple machines more deeply.

First, Second, and Third Class Levers