Energy Practice NAB

Today we did a practice NAB for your NAB on 27/9/11.  The questions are below and the answers in the pictures at the bottom with the mark allocation drawn on.

Energy Practice NAB

1. A sprung train barrier stops a 2000kg train traveling at 10m/s.  On impact the train exerts a force of 400kN on the barrier.  Calculate the following:
  a) The kinetic energy of the train before it hits the barrier
  b) The compression of the spring in the barrier once the train has stopped moving
  c) The speed of the train once it has collided with the barrier and continued to move after 100mm.

2. An energy audit is carried out on an electrical kettle connected to a 240V supply. The heating element has a resistance of 50Ω and the kettle took 3 minutes to boil 2 litres of water from a starting temperature of 80°c.  Calculate:
  a) The electrical energy going into the kettle
  b) The heat energy produced by the kettle
  c) The energy "lost"
  d) The efficiency of the system

These questions are of the same standard as the NAB, if you are happy with these and how to answer them you will be prepared for the NAB.  Revision of the homework is also a good way to ensure a thorough understanding.  If you were off today at FutureWise then I strongly suggest you come and get your homework marks back!

Here are the answers: