# Science 4.11th Flashcards

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1

How much work is done by someone pushing a 500N crate 50 meters across the floor?

w=Fd

w=500N*50m

w=25,000 J

2

Why would someone use a machine with a mechanical advantage of 1? Give an example and explain why it is used.

A machine not only decreases the input force, but also changes the direction of the input force. In a single pulley, the force is applied downward to lift the object up so the person may use their body weight to help.

3

Why do work and energy have the same label? What is that label?

Energy is the abillity to do work so the label is the same for both. The label is Joules (J)

4

Explain why mechanical advantage does not have a label.

Mechanical Advantage is a ratio. When dividing the forces the label of Newtons cancel.

5

What does it mean to have a mechanical advantage of greater than 1?

The output force of the machine is greater than the input force of the person using the machine.

6

What is the difference between no net work and no work?

NO WORK MEANS THAT THERE IS NO FORCE THAT HAS AFFECTED THE DISPLACEMENT OF AN OBJECT. NET WORK IS WHEN 2 OR MORE FORCES ARE AT PLAY THAT AFFECT THE DISPLACEMENT OF AN OBJECT AND OFFSET EACH OTHER.

7

WHAT IS THE WORK DONE BY SOMEONE HOLDING A 50 GRAM TEACUP 2 METERS OFF THE GROUNC?

w=Fd

w-0.050 kg9.81 m/s20m

w=O J

8

IS MORE WORK DONE WITH OR WITHOUT A RAMP? EXPLAIN

...

9

WHAT HAPPENS TO THE INPUT FORCE WHEN MORE PULLEYS ARE ADDED TO THE SYSTEM - EXPLAIN

THE INPUT FORCE DECREASES BECAUSE THE STRING PULLED IS A FARTHER DISTANCE TO COMPENSATE FOR EQUAL WORK.

10

WHAT HAPPENS TO THE WORK WHEN MORE PULLEYS ARE ADDED TO THE SYSTEM

THE WORK IS THE SAME IF THE FRICTION IS NEARLY ZERO BECAUSE THE FORCE DECREASES WHILE THE DISTANCE INCREASES

11

WHAT IS THE RELATIONSHIP WORK AND POWER?

POWER IS HOW QUICKLY WORK IS DONE

12

A FORCE THAT OPPOSES THE MOTION

FRICTION

13

A FORCE THAT AFFECTS THE DISPLACEMENT OF AN OBJECT

WORK

14

IF YOU WANT TO DECREASE THE INPUT FORCE OF A FIRST CLASS LEVER, WHAT SHOULD YOU DO WITH A FULCRUM. EXPLAIN

MOVE THE FULCRUM CLOSER TO THE LOAD. THIS WILL INCREASE THE DISTANCE THE INPUT FORCE TRAVELS WHICH WILL DECREASE THE FORCE INPUT.

15

THE SPEED AT WHICH WORK CAN BE DONE

POWER

16

A PUSH OR A PULL ON AN OBJECT

FORCE

17

WHEN A PULLEY IS USED, THE SUPPORT MUST HOLD HOW MUCH WEIGHT RELATIVE TO THE WEIGHT BEING LIFTED

DOUBLE THE WEIGHT

18

EXPLAIN WHY A PENDULUM STOPS MOVING AFTER A PERIOD OF TIME. WHAT HAPPENS TO THE ENERGY?

THERE IS FRICTION AT THE LOCATION WHERE THE PENDULUM PIVOTS. THE FRICTION TRANSFERS THE MECHANICAL ENERGY INTO THERMAL ENERGY. BECAUSE THE MECHANICAL ENERGY IS DECREASING THE PENDULUM SLOWS UNTIL IT EVENTUALLY STOPS WHEN ALL THE MECHANICAL ENERGY HAS BEEN TRANSFERRED INTO THERMAL ENERGY.

19

ABILITY TO DO WORK

ENERGY

20

IF YOU WANT TO DECREASE THE FORCE WHEN USING A RAMP, WILL YOU USE A LONGER RAMP OR A SHORTER RAMP? EXPLAIN

LONGER RAMP SO THE DISTANCE IS INCREASED AND THE FORCE IS DECREASED

21

WHAT ARE TWO BENEFITS THAT A SIMPLE MACHINE CAN OFFER?

CHANGES THE DIRECTION OF THE INPUT FORCE. DECREASES THE AMOUNT OF INPUT FORCE.

22

WHAT IS THE MOMENTUM OF A 100 KG OBJECT TRAVELING 45 M/S NORTH?

p=mv

p=100kg*45m/s

p=4500 kg* m/ss North