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ENGINEERING, PPT 2018 HSC 26c

The top view of a fidget spinner is shown.
 

What force Q is required to overcome the 20 N resistance force shown?   (3 marks)

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`2.86\ text{N}`

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Actual diagram used to calculate the 35 mm distance below.

`sumM` `=0`  
`d` `=35\ text{(from scale drawing)}`  
`Q xx d` `=20 xx 5`  
`Q` `=100/35=2.857…`  

  
`:.\ Q = 2.86\ text{N}`


 
♦♦♦ Mean mark 27%.

ENGINEERING, PPT 2020 HSC 23b

A diagram of the front steering system of a bicycle is shown.
 


 

  1. A rider leans forward so that 55% of their mass is exerted as a force, as shown in the diagram. A turning moment of 132.19 Nm is generated about the front axle.
  2. What is the mass of the rider?   (3 marks)
  1. In overcoming the resistance due to gravity, drag and rolling resistance, a rider applies a force of 500 N on the pedals. This allows the rider to cover, in 5 seconds, a distance of 20 metres from the starting point.
  2. How much power was produced by the rider?  (2 marks)
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i.   `95\ text{kg}`

ii.  `2000\ text{W}`

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i.  
         

`sin20°` `= d/740`  
`d` `= 740 xx sin20°= 253.09\ text{mm}`  

 

`M` `= Fxxd`  
`F` `= 132.19/0.25309= 522.5\ text{N}`  

 

`55\text{%} xx F_(text{total})` `= 522.5\ text{N}`  
`F_(text{total})` `= 522.5/0.55= 950\ text{N}`  

 
`:. M_(text{rider})= 950/10= 95\ text{kg}`


♦ Mean mark 47%.

ii.   `F=500\ text{N}, \ s=20\ text{m},\ t=5\ text{sec}`

`P` `= Fxxv`  
  `= F xx s/t`  
  `= 500 xx 20/5`  
  `= 2000\ text{W}`