Physical Science- Chapter 14
Ideal mechanical advantage
A machine's___is the mechanical advantage in the absence of friction.
Lever
A screwdriver used to pry the lid off a paint can is an example of a(n)_.
Pulley
A simple machine consisting of rope fitted into a groove in a wheel is a(n)_.
Inclined plane
A slanted surface along which a force moves an object to a different elevation is called a(n)_.
A wheel and axle is a simple machine that consists of two disks or cylinders, each one with a different radius.
Describe a wheel and axle.
A machine makes work easier to do by changing a force.
Describe what a machine is able to do.
Work is maximized when force is applied in the same direction that the object is moving.
Describe what conditions of force and motion result in maximum work done on an object.
Power
In order to do work faster, more_is required.
Force
In science, work is done when a(n)_acts on an object in the direction the object moves.
1. Lever 2. Wheel and axle 3. Inclined plane 4. Wedge 5. Screw 6. Pulley
List the six types of simple machines.
Efficiency
Percentage of work input that become work output
Increases
Reducing friction_the efficiency of a machine.
Ideal mechanical advantage
Screws with threads that are close together have a greater___.
Watt
The SI unit of power is the_.
Joule
The SI unit of work is the_.
Fulcrum
The fixed point that a lever rotates around is called the_.
Output
The force exerted by a machine is called the_force.
Mechanical advantage
The number of times a machine increases force
True
True or false. A compound machine is a combination of two or more simple machines that operate together.
True
True or false. A machine can make work easier to do by changing the size of the force needed, the direction of a force, or the distance over which a force acts.
True
True or false. An inclined plane is an example of a machine.
True
True or false. Power is the rate of doing work.
1. A car 2. A washing machine 3. A watch
What are some examples of a compound machine?
Air resistance
What is a significant factor affecting a car's fuel efficiency?
The amount of force exerted on a machine.
What is the definition of an input force?
Because there is always friction that must be overcome.
What is the efficiency of a machine less than 100 percent?
You can increase power by doing a given amount of work in a shorter period of time. When you do less work in a given time period, the power decreases.
What is true about power?
Horses were a logical choice for comparison as they were the most commonly used source of power in the 1700s.
Why did James Watt use the power output of a horse to compare the power outputs of steam engines he designed?
Because in order for work to be done on an object, the object must be moving.
Why isn't work being done on a barbell when a weight lifter is holding the barbell over his head?
Work input equals the input force multiplied by the input distance.
Write a word equation that describes work input.