his slides concerning with concept of work done for form one students

1. PHYSICS LESSON
SUBJECT: PHYSIC
CLASS LEVEL : FORM ONE
TOPIC :
CONCEPT OF WORK DONE
YOUR TEACHER:
MWEMA ISSA MWEMA

2. CONCEPT OF WORK
In order to do work three things are
needed
ENERGY APPLIED FORCE DISTANCE MOVED BY A BODY
WORK DONE

3. Work can be defined as a product of the force
applied on body and the distance moved by
body
𝑤. 𝑑 = 𝑭(𝑁) × 𝑑(𝑚)
Where force 𝑭 = 𝐹 cos 𝜃
𝑤. 𝑑 = 𝐹 𝑐𝑜𝑠 𝜃 × 𝑑
Where 𝜃 direction of applied force
𝒘. 𝒅 = 𝑭 𝒅 𝒄𝒐𝒔 𝜽
This is general formula of work done

4. Maximum and Zero work done
Maximum work done
𝒘. 𝒅 = 𝑭 𝒅 𝒄𝒐𝒔 𝜽
Work done will be maximum when force acts on
angle θ = 0
w. d = F d cos θ = Fd cos 0
cos 0 = 1
Since the maximum work done calculated by
formula
𝒘. 𝒅 = 𝑭𝒅
the work done is measured in Nm or Joules

6. • Zero work done, it occurred under two
conditions
𝒘. 𝒅 = 𝑭 𝒅 𝒄𝒐𝒔 𝜽
• If force act on a body is perpendicular to
motion of an object θ = 90 ,
𝑤𝑑 = 𝐹 𝑑 𝑐𝑜𝑠 90 = 𝟎 𝑱𝒐𝒖𝒍𝒆𝑠
force
displacement

7. • When force applied on object, and it remain
at its rest position( no displacement) i.e.
when 𝒅 = 𝟎 𝒎
• 𝐰. 𝐝 = 𝐅 × 𝟎 = 𝟎 𝐉𝐨𝐮𝐥𝐞𝐬

8. WORKED EXAMPLE
A man lifts a heavy load with a force of 200N, Calculate
maximum work done if he rise it to 1.5 m.
Given data
Applied force 𝐅 = 𝟐𝟎𝟎 𝐍
Displacement in which load lifted 𝐝 = 𝟏. 𝟓 𝐦
Work done = ?
Solution
From the formula 𝐰𝐨𝐫𝐤 = 𝐅 × 𝐝
𝐰𝐨𝐫𝐤 = 𝟐𝟎𝟎𝐍 × 𝟏. 𝟓𝐦
work done = 30 Joules

9. Practical problems
1. Calculate the work done when a 10kg object
is lifted to height of 5m above the ground.
2. If your mass is 45 kg , how much work would
you do in climbing a ladder that is 10m height.
3. Let an object is dropped and falls to the
ground surface.
a. Is a work done while it falling ?
b. If so, what the force did work ?
c. Was work done on or by the object ?
Hint 𝐅 = 𝐦𝒈 and 𝒈 =10N/kg

10. If will be there any contradiction or miss
understand about ,please contact with me on
Gmail account isamwema@gmail.com or phone
number +255776863549