Net work equals change in kinetic energy

Steps:

• Apply work-energy theorem: net work on suitcase = ΔKE.
• For constant speed (A, B, D), ΔKE = 0, so net work = 0.
• For C, increasing speed on frictionless slide means ΔKE > 0, so net work > 0.
• Distances irrelevant since net work depends on speed change, not path length.

Why C is correct:

• Frictionless slide allows gravity to accelerate suitcase downward, increasing KE per work-energy theorem (W_net = ΔKE > 0).

Why the others are wrong:

• A: Constant speed up slope means net force = 0, so W_net = 0.
• B: Constant vertical speed means net force = 0, so W_net = 0.
• D: Constant horizontal speed with negligible resistance means net force = 0, so W_net = 0.

Final answer: C