Teacher's notes and answers to questions in the book - Hodder Plus ...

WJEC GCSE Additional Science Teacher’s Notes
17
The physics of rugby
_ Energy and work (pages 189–92)________________
Questions
1. What is meant by ‘work done’
Work is done when energy changes form.
2. What are the units of work done
Joules
3. What factors dictate the amount of work done by a player in a lineout lifting a jumper
Number of players lifting the jumper, weight of the jumper, distance lifted.
4. In a driving maul, players pushing to drive the maul forward typically push with an average force of
750 N. If the driving maul is pushed 8 m, how much work does a typical player do
work done = force × distance = 750 × 8 = 6000 J
5. During a scrum (Figure 17.3), eight players each push with an average force of 600 N, moving the
scrum 2.5 m.
a What is the total force exerted by all eight players
total force = 8 × 600 = 4800 N
b Calculate the total work done moving the scrum.
work done = force × distance = 4800 × 2.5 = 12 000 J
6. In a head-on driving tackle, a rugby player does 1650 J of work driving the opponent backwards by 3 m.
Calculate the force of the tackler.
work done = force × distance
work done 1650
force 550 N
distance 3
7. Calculate the distance that a line-out jumper is lifted if the player lifting the jumper exerts a force of
950 N and does 1520 J of work.
work done = force × distance
work done 1520
distance 1.6 m
force 950
8. What is meant by the efficiency of an energy transfer
Efficiency is a measure of how much useful energy comes out from an energy transfer
compared to how much total energy goes in.
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