Question

2. It is weigh-in time for the local under-85-kg rugby team. The bathroom scale used to assess eligibility can be described by Hooke’s law and is depressed 0.75 cm by its maximum load of 120 kg. (a) What is the spring’s effective spring constant? (b) A player stands on the scales and depresses it by 0.48 cm. Is he eligible to play on this under-85 kg team?

Please include all of your steps.

Answer 1

• Weight=mg=120(9.8)=1176N

Apply hooke's law

$\\ \rm\rightarrowtail F=kx$

$\\ \rm\rightarrowtail 1176=k(0.0075)$

$\\ \rm\rightarrowtail k=156800N/m$

#b

We need mass again

$\\ \rm\rightarrowtail F=kx$

$\\ \rm\rightarrowtail mg=kx$

$\\ \rm\rightarrowtail 9.8m=156800(0.0048)$

$\\ \rm\rightarrowtail 9.8m=752.64$

$\\ \rm\rightarrowtail m=76.8kg$

• He is e eligible