Work done question. No idea?

a)
Force in the direction of the motion = 12 N

Energy transferred (Work done) = F s = 12 × 4.0 J = 48 J


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b)
Force in the direction of motion = (12 N) × cos60° = 6 N

Energy transferred (Work done) = F s = 6 × 4.0 J = 24 J


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c)
Force in the direction of motion = (12 N) × cos90° = 0

Energy transferred (Work done) = F s = 0 × 4.0 J = 0 J

Always net force in the direction. F(net vector) times d's vector. It's that simple. It's only complicated if the force or direction changes. like a roller coaster, for example.

With a constant force and constant direction of motion, W = F d cos(θ)

More generally, W = ∫ F • dx
• means the vector dot product. A • B is the magnitude of A times the component of B in the direction of A. (Or vice versa; it's commutative.)

The confusing part is that the question implies this force causes the object's motion. There must be other forces and/or momentum involved. This is how much work is done by gravity when an object (a) falls straight down, (b) slides down a 30° incline, or (c) is in a circular orbit.