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

WJEC GCSE Additional Science Teacher’s Notes
8. The value of g is approximately 10 N/kg. How close to this value is:
a your average calculated value
b the gradient of your graph
Calculated deviations from 10 N/kg should be very small.
9. How could you use your graph to determine a value of the uncertainty of the value of g
Plot range bars and get a range of different ‘best-fit’ lines (maximum/minimum/best-fit).
10. Why is it more accurate to measure the weight of a slotted mass with a Newton meter with the
lowest range capable of measuring it
Lower ranges will have greater precision.
11. Would it be better to measure all the weights with the same (bigger ranged) Newton meter
This leads to an interesting discussion of precision v zero-ing errors. Answer: depends on
the quality of the Newton meter.
Discussion point
When we are living in the Earth’s gravitational field we live in a world of 1 g, that is, 1 × the Earth’s
gravitational field. At take-off, the astronauts experience 3 g (3 × the Earth’s gravitational field strength). In
orbit, the astronauts effectively experience 0 g. What do you think these gravitational fields ‘feel’ like
There is an interesting interview with Dr Mae Jemison (STS-47 Shuttle Endeavour 1992):
http://teacher.scholastic.com/space/mae_jemison/interview.htm
Questions
1. A typical ISS module has a mass of 22 700 kg. Each of the two Space Shuttle solid rocket boosters has
a lift-off mass of 590 000 kg, and the external fuel tank (filled with rocket fuel) has a lift-off mass of 760
000 kg.
a Calculate the weight of each component of the Space Shuttle launch system.
Space Shuttle: mass = 78 000 kg weight = 780 000 N
ISS Module: mass = 22 700 kg weight = 227 000 N
Solid rocket booster: mass = 590 000 kg weight = 5 900 000 N (×2 = 11 800 000 N)
External fuel tank: mass = 760 000 kg weight = 7 600 000 N
b What is the total lift-off weight of the Space Shuttle launch system
Total weight at take off = 20 407 000 N
c
What is the minimum total thrust needed by the Space Shuttle main engines and the solid fuel
rocket boosters Why is this a ‘minimum’
Minimum thrust = total weight = 20 407 000 N
The total thrust of the engines does not act directly downwards – some of the thrust acts at
an angle to the vertical as the combustion products come out of the jet engines.
2. The last Space Shuttle launch took place in June 2011. From that point on, the ISS will be serviced via
Russian Progress and American Dragon spacecraft whilst astronauts will travel to and from the ISS in
Russian Soyuz spacecraft. All Russian spacecraft are launched via Soyuz-2 rockets and the American
spacecraft will be launched with Falcon 9 rockets (Table 16.2). Copy and complete the table,
calculating the launch weight of each rocket and the minimum resultant upwards force at launch.
62