Physics Textbook Questions: Energy & Work (pg 9)

a) i) A rower moves the oars, covering muscular chemical energy to kinetic energy and a little heat energy due to friction. This is transferred to the waterm where kinetic energy makes small waves, which push the boat forwards.
ii) A car park barrier converts electrical energy into mechanical and then kinetic energy to move, and gains GPE as it rises, which is then converted back to kinetic as it lowers.

b) 3000N x 50m = 150,000 J

a) Brake pads warm up after breaking as the friction from the callipers rubs the waning kinetic energy from the wheels and heats it up as an every transfer.

b) 7000N x 20m = 140,00J

a) i) 20N x 4.8m = 96J
ii) 80N x 1.2m = 96J

b) 1400J / 7m = 2000N

a) 25N x 12m = 300J

b) The student converts muscular chemical energy into kinetic energy as they push the box along. The box gains kinetic energy but wastes some as heat due to friction and some sound.