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A horizontal spring with spring constant 85 n/m extends outward from a wall just above floor level. a 9.5 kg box sliding across a frictionless floor hits the end of the spring and compresses it 6.5 cm before the spring expands and shoots the box back out. how fast was the box going when it hit the spring?

Respuesta :

shinmin

Spring constant: 85N/m, 9.5kg box, compresses spring 0.035m. 

85N/m* 0.035m = 2.975N 


Use spring equation 1/2*k*(change in distance) ^ 2 


1/2*85N/m*(0.035m) ^ 2=0.052063J 


Now use kinetic equation:

1/2*m*v^2 
0.052063J=0.5*9.5kg*v^2 
v = 0.1047 m/s

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