Science Chapter 12 *ALL (SUMMERS) ANSWERS PLUS THE LAST QUESTION*
What is a machine?
A device that allows you to do work in a way that is easier
What is an ideal machine?
A machine with an efficiency of 100% and is not affected by friction
What is a joule?
A unit of work equal to one newton-meter
How can you increase a pulley's mechanical advantage?
By increasing the number of sections of rope
How can you determine the amount of work done on an object?
By multiplying force times distance
How does a screwdriver make work easier?
By multiplying input force and increasing distance
In what three ways can machines make work easier?
Change amount of force exerted, the distance over which a force is exerted, or the direction in which force is exerted
What type of simple machine is a door stopper? Rake? Windmill? Slide?
Door stopper-wedge Rake-lever Windmill-wheel and axel Slide-inclined plane
List the six kinds of simple machines.
Inclined plane, wedge, screw, lever, wheel and axel, and pulley
What is the ideal mechanical advantage of each type of simple machine?
Inclined plane: length of incline/height of incline Wedge: length/width Screw: length around threads/length of screw Lever: distance fulcrum to input force/distance fulcrum to output force Wheel and axle: radius of wheel/radius of axel Pulley: number of sections of rope
What is the mechanical advantage of a machine?
Mechanical advantage = output force/input force
If a machine has an input force of 40N and an output force of 80N, what is its mechanical advantage?
Mechanical advantage = output force/input force = 80N/40N = 2
What must you know in order to calculate a machine's efficiency?
Output and input work
Your laundry basket weighs 22N and your room is 3.0m above you on the second floor. It takes you 6.0 seconds to carry the laundry basket up. What is you're power?
Power = force × distance/time = 22 × 3/6 = 66/6 = 11w
If you take only 4.4 seconds to carry the basket upstairs, what is your power?
Power = force× distance/ time = 22×3/4.4 = 66/4.4 = 15w
What is power?
Power = work/time = force × distance/time
How are power and work related?
Power equals the amount of work done on an object in a unit of time.
In which of the following situations is work being done: rolling a bowling ball, pushing on a tree for ten minutes, or kicking a football?
Rolling a bowling ball and kicking a football
What is the mechanical advantage of a machine that changes only the direction of the applied force?
The input and output forces will be the same so it will always be 1.
In order for work to be done on an object, what must happen to the object?
The object must move.
Is more work done when a force of 2N moves an object 3m or when a force of 3N moves an object 2m?
The same amount of work is done on both objects because Work = force × distance = 3 × 2 = 6
How is a real machine like an ideal machine, and how is it different?
They both do work, but the efficiency of an ideal machine is 100%. Because of friction, the efficiency of a real machine is less than 100%.
How is calculating the ideal mechanical advantage of an inclined plane similar to calculating that of a screw?
They work in similar ways and a screw is an inclined plane wrapped around an axel.
How many simple machines are needed to make a compound machine?
Two or more performing the same task
What is work?
Work = force × distance
How do you find the mechanical advantage of a compound machine?
You add the ideal mechanical advantages of the two implement machines
Can you consider your thumb to be a lever? Why or why not?
You can because your knuckle is like a fulcrum and it bends and rotates like a lever and you can pry things open with it.
