Work energy and power from class 9th

1. WORK –
ENERGY
PRINCIPLE

2. –What is work?
–What is energy?

3. LET’S DO A PROBLEM
– An object of mass ‘m’ moves with a velocity ‘u’.
When a force is applied in the direction of motion
its acceleration becomes ‘a’. If ‘s’ is the
displacement of the object in the direction of force.

4. LET’S DISCUSS
– What is the work done by the force?
– What is force given by Newton’s second law of
motion
– Then what is work?
– What is the 2nd equation of motion?

5. -From this equation, what is 𝑣2
− 𝑢2
?
-What is acceleration?
-Derive the equation for work done?

6. consolidation
–Work done = change in the Kinetic
Energy
–This is Work-Energy Principle/
– 𝑤 =
1
2
𝑚𝑣2
−
1
2
𝑚𝑢2

7. LET’S DO A PROBLEM
– A body of mass 2kg is kept at rest. If a force
of 5N is applied on it for 10s, what will be
the work done?

8. LET’S DISCUSS
– What is the mass of the object?
– What is the force applied on the object?
– What is the duration of force applied?
– What is the initial velocity of the object?

9. – What is work- energy principle?
– What is the equation of force?
– What is the acceleration from this equation?
– Find the value of final velocity v
– Then find the work done?

10. Work –Energy principle states that work
is the rate of change of Kinetic Energy

11. A body of mass 5kg has a initial velocity 0 and final
velocity 10 m/s. If a force of 5N is applied on it for
5s. What will be the work done?

12. m= 5kg a=F/m = 5/5 =1 𝑚 𝑠2
U= 0 𝑤 =
1
2
𝑚𝑣2 −
1
2
𝑚𝑢2
V=10 m/s
F= 5N