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1. A clerk pushes a filing cabinet of mass 22 kg across the floor by exerting a horizontal force of magnitude 98 N. The magnitude of the force of kinectic friction is acting on the cabinet is 87 N. The cabinet starts from rest. Use the law of conservation of energy to determine the speed of the cabinet after it moves 1.2m.

Heres what i did but i don't i used the law of conservation of energy.

W= Ek2 - Ek1

Fd=1/2mv^2

Fapplied - Ffk=1/2mv^2

I am not going to show all the steps but i after manipulating that formula i got 1.1 m/s. The answer is right, but i dont know if that's how your supposed to do it.

2. A 0.20 kg mass is hung from a vertical spring of force constant 55 N/m. When the spring is released from its unstretched equilibrium position, the mass is allowed to fall. Use the law of conservation of energy to determine

a)The speed of the mass after it falls 1.5 cm

b)The distance the mass will fall before reversing direction.

I did (a) easily and got the right answer which is 0.48 m/s. But i cant seem to get the right answer to be which is 0.071 m

Here's what i did.

Fe=Fg

kx=mg

x=mg/k

x=0.0356 m

Did i do something wrong. Can you please help me anyone. I think i will have another question when i get to it.