A motor pulls a crate along a straight, level track. It applies 80 N for the first 2.0 m and 50 N for the next 4.0 m. A constant frictional force of 30 N acts throughout. What is the increase in the kinetic energy of the crate?
120 J120\ \mathrm{J}120 J
360 J360\ \mathrm{J}360 J
540 J540\ \mathrm{J}540 J
180 J180\ \mathrm{J}180 J
115 exam-style questions on Edexcel GCSE Physics 8.1 Energy transfers and work, covering 8.1.1 Energy stores and transfer diagrams, 8.1.2 Ways of changing a system's energy, and 8.1.3 Work done by forces. Each one has a worked solution and a mark scheme showing where the marks go.