Class 9th – WORK

• Work is defined as the force acting upon an object that causes an object to move.
• It is defined as the product of the magnitude of force and the displacement due to force.
                 W=F x s

Here,    W= work done on an object
            F = Force on the object
            s = Displacement of the object

• Work done depends upon 2 factors
• Force: greater the force, greater the work done.
• Displacement: greater the displacement, greater the work done.
• When F=1N and s=1m then the work done will be 1Nm or 1J
• 1 Joule is defined as the work done by an object when 1N Force is applied on that object and the object is displaced by 1m.

• Work is Scalar physical quantity.

• Work done is of three types.

POSITIVE WORK:  

• When force and displacement acts on the same direction, then the work is said to be positive work.
• In positive work, force applied by the object and displacement produce follows the same path.

• When the value of angle (Ɵ) is less than 90°, the work is said to be positive.

NEGATIVE WORK

• When force and displacement acts on the opposite direction, then the work is said to be negative work.
• In negative work, force applied by the object and displacement produce follows the opposite path.
• In this case, displacement is opposite to the direction of force.

Zero work done

• When the displacement is perpendicular to the work done then the work done is said to be zero.
• When the value of angle (Ɵ) is equal to 90°, the work is said to be zero.

•   W= 0 as cos90°=0, therefore, work done is zero.