A car of mass 1000 kg takes a bend of radius 50 m at 10 m per second. The centripetal force needed is

  • A. 200 N
  • B. 2000 N
  • C. 5000 N
  • D. 10000 N

Explanation

The force is mv squared over r, which is 1000 times 100 divided by 50, giving 2000 N. On a level road this force must come from friction between the tyres and the surface, so if the required force exceeds the maximum friction available the car skids outwards. Doubling the speed would quadruple the force, which is why bends are so much more dangerous at speed.

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