# Physics homework help?

Help please

Spiderman uses his spider webs to save a runaway train moving about 50 km/h. His web stretches a few city blocks (500 m ) before the 10000-kg train comes to a stop. Assuming the web acts like a spring, estimate the effective spring constant.

### 2 Answers

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- Anonymous1 year ago
Energy conservation shall apply :

KE = SPE

m*V^2 = k*x^2 ...where x represents web's stretching

k = m*V^2/x^2 = (10^4*50^2/3,6^2) / (5^2*10^4) = 100/3,6^2 = 7.716 N/m

- DylanLv 61 year ago
Energy conversation.

0.5*m*v^2 = 0.5*k*x^2

k = mv^2/x^2

= 1000*(50 km/h *1000 m/km / 3600 s/h)/500^2

= 0.05556 N/m

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