Energy · 01 / 05

Work & Energy Transfer

A force transfers energy through displacement only to the extent that the force points along the displacement.

The learner question

When does a force actually transfer energy?

The geometry matters. A perpendicular force can be large and still do zero work; an opposing force does negative work.

Core relationship
W=FdcosθW = Fd\cos\theta

Work = parallel force component × displacement.

Transfer lab

Rotate the force relative to the displacement.

θ = 0°
displacement 4.0 m
force 12 N
parallel force
12.0 N
work
48.0 J
meaning
energy enters the motion
Force12 N
Displacement4.0 m
Angle0 °
Curated cases
Boundary

A support force can be real and large while doing zero work if the displacement is perpendicular to it.

Transfer check

A satellite moves tangent to its circular orbit while gravity points inward. What work does gravity do at that instant?