Work

What is mechanical work (W)?

• Energy is transferred to or from an object via the application of force along a displacement

• Scalar quantitiy

• Units: Nm = J

Equation for mechanical work (constant velocity)

W=FscosΘ

• W is work

• F is the force

• s is the displacement

• Θ is the angle in between them

*Magnitudes

When is work zero?

• When the Force and displacement are perpendicular (90 degrees)

• When Force is zero

• When displacement is zero

• No work occurs when an object moves on a frictionless surface at a constant velocity (thus with no horizontal force acting on it)

Describe F-s graphs

• The force-position (F-s) graphically shows the work done by a force on an object

• y-axis: force on an object

• x-axis: displacement

• Used when the force and displacement are parallel (in the same or opposite direction)

• Work = the area under the F-s graph = FscosΘ

*Assume that the force acts in the same direction or opposite direction as the displacement

How does F-s graph look when there is a constant force

Straight horizontal line (slope =0)

How does F-s graph look when there is a changing force

Linear line with a positive or negative slope (uniformly increasing force)

• Work = the area under the F-s graph = F_averagescosΘ