Forces, Work, Energy

Work, Force and energy

by Hamsa Mahesh

​Why is work not work ?

• ​We can see person 1 lifting person 2 but this cannot be called as work.

• ​Force is being apllied but the object lifted is not being displaced.

• ​90 degree law

​2 CONDITIONS FOR WORK TO WORK

​1. There should be a force applied.

​2. The abject should get displaced.

​

​FORMULA OF WORK:

​As we know if even one of force or displacement is 0 then work will also be 0.

​Direction of force

​work= f*s

​f= vector

​s=vector

​w= scalar

​

Multiple Choice

SO, what is the formula of work?

• w=f*s

• w=f+s

• w=f/s

• w=f-s

​SI unit of work

​YES, NOW WE KNOW THAT W=F*S BUT WHAT WILL THE SI UNIT BE?

​

​W=F*S

​F= NEWTONS

​S= METERS

​W??

Multiple Choice

SI unit of work is?

• MN

• GF

• FG

• NM

​ENERGY

​When an object has the capability to do work it is said to have energy.

​

​The abject which does

​the work loses the

​energy but the object

​on which work is done

​gains the energy.

​

​The energy from the former is passed on to the latter.

​Any object with

​energy can do work.

​

​THEREFORE SI UNIT

​OF ENERGY IS ALSO

​JOULES.

​

​1 J of energy can do 1 J of work. 1kJ=1000 J

​

​Person a is moving slowly when compared to person b.

​They both have gained kinetic energy and more the speed they have more the k_E.

​The kinetic energy of a body which is moving with certain velocity is always equal to the work done it to make it aqquire that velocity.

​derivation of kinetic energy

​PAINT

​Potential energy.

​Energy gained by the object due to the virtue of its posotion.

​U=mgh

​

​PAINT

​

​The girl here is

​holding the bow stretched

​which puts potential energy

​in it.

​Energy can be converted

​But the energy cannot

​be created or destroyed

​Power

• ​There is a lot of pwer in energy here.

• ​Power= rate if doing work

• ​p=w/t

• ​p=mgh/t

• ​p=fs/t

​SI unit of power is watts which is also called joules.

​1KW=1000WATTS

1000 J/S

​

​Commercial unit

​1 joules/watt is too small so we use 1kw h.

​1 kw h= 1kw*1hr

​=1000w*60*60

​=1000w*3600s

​=3600000 J/W

​1kwh=3.6*10^6 J or W

​

​