Mechanics

Question 1

Explain with regard to Newtons laws why air exerts a force on a jet engine.

Answer 1

There is a force due to a change in momentum of the air - f= mv/t
force of air in is a third law pair with the thrust of the plane.
Opposite direction same magnitude.

Question 2

Does mass affect Terminal V

Answer 2

No - affects acceleration. Only SA affects TV

Question 3

How would you compare the mechanical properties of 2 wires

Answer 3

Need length
change in length
Force
Area
Young’s modulus

Put wires on M rules, fixed measure point to determine change in length
Measure Diameter in 3 placed and take avg
Connect masses, F=MG
repeat w different masses and for the unloading process
Repeat with each wire

Question 4

What is the gradient of a distance time graph

Answer 4

instantaneous velocity

Question 5

Why would xénon atoms with a lower specific charge be a better propellant than Helium?

Answer 5

Helium is a lighter atom
Helium would gain more speed, but are significantly lighter
therefore less momentum change
therefore less thrust and He less effective

Question 6

Tensile stress definition

Answer 6

Force applied per cross sectional area

Question 7

Tensile strain definition

Answer 7

extension over original length

Question 8

Why is error from a metre rule 2mm

Answer 8

+- 1mm at each end, add errors together

Question 9

How does increased reflectance increase acceleration with a solar sail?

Answer 9

More reflectance means a greater change in momentum. Change in momentum means a large force and larger acceleration