4.1 - Work(15pts.)

Approximately how much work do you do (in Joules) when you lift your 10.0 kg sister to a height of 1.5 m?

NOTE: MASS x GRAVITY = WEIGHT [F_G]

[NUMBER ONLY/ NO UNITS]

Mathematical Equivalence

ON

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HS-PS2-1

Learning Target 2

A particular lever is 90.0% efficient. If 50.0 J of input work are done on the lever, then how much output work does the lever do, on its load?

[NO UNITS/ NUMBER ONLY]

Mathematical Equivalence

ON

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HS-PS2-1

Learning Target 2

The mechanical advantage of a pulley system is 4.00. Using this pulley system, how much force do you need to exert to lift a 500.0 N box?

[Reminder: Pulleys REDUCE force through Mechanical Advantage]

[NO UNITS/ NUMBER ONLY]

Mathematical Equivalence

ON

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HS-PS2-1

Learning Target 2

Which simple machines represent variations of an inclined plane? [Select all that apply]

• wedge

• wheel and axle

• lever

• pulley

• screw

Answer explanation

The simple machines that represent variations of an inclined plane are the wedge and the screw.

Which factor increases as the efficiency of a machine increases? [MORE EFFICIENT]

• More input work

• More output work

• Friction

• Air Resistance

Answer explanation

As the efficiency of a machine increases, more output work is produced, which is the factor that increases.

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HS-PS3-3

It takes 600 J of work to lift a person up but 1200 J to push that person up a ramp to the same height.

What is the efficiency of the ramp?

• 0%

• 25%

• 50%

• 100%

Answer explanation

Efficiency is calculated as (work output / work input) * 100%. Here, work input = 1200 J, work output = 600 J, so efficiency = (600/1200) * 100% = 50%

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HS-PS2-1

An input force of 80 N is used to lift an object weighing 240 N with a system of pulleys. What is the mechanical advantage of the pulley system?

• 1

• 3

• 0.33

• 19,200

Answer explanation

The mechanical advantage of the pulley system is calculated by dividing the weight being lifted by the input force, which gives 240 N / 80 N = 3.

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HS-PS3-3

Organize these machines by how they are useful.

Groups:

(a) Increases Speed

,

(b) Changes Direction of Force

,

(c) Increases Force

• 
• 
• 
• 

Tags

HS-PS3-3

What percent of Work is done at 60^o?

• 10%

• 35%

• 50%

• 0%

Answer explanation

50% of work is done at 60° because it is halfway through the total work, making it the correct choice.

Tags

HS-PS3-3

What percent of Work is done at 90^o?

• 10%

• 35%

• 50%

• 0%

Answer explanation

The correct answer is 0% because work done at 90 degrees is zero in physics as the force and displacement are perpendicular.

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HS-PS3-3