Friction and dragIB MYP Physics: Mind map

Exam questions on Friction and drag

1. Cyclists in Rotterdam fit rubber brake pads that press against the metal rim of a wheel to slow the bicycle down. A cyclist notices that her brakes work much less well on a rainy day, and that her bicycle chain needs a little oil to run smoothly.
   Explain how putting oil on the bicycle chain reduces the energy wasted as it moves.2 marks
2. A student in Cairo tries to push a heavy wooden box across a concrete floor. She pushes with a gradually increasing force. At first the box does not move at all, then it suddenly starts to slide, and she finds it easier to keep it sliding than it was to get it moving.
   Suggest one change the student could make so the box is easier to slide, and explain why it works.2 marks
3. A skydiver in Queenstown, New Zealand, jumps from an aeroplane and falls with her parachute closed. After about 12 seconds her speed stops increasing and stays at a steady 55 m/s. Later she opens her parachute and, a few seconds after that, she is falling at a steady 5 m/s until she lands.
   Explain why the skydiver stops accelerating after about 12 seconds, even though she is still falling.3 marks