A 12kg box is pulled 3.00m to the right along the floor by applied force F_A at

Question

A 12kg box is pulled 3.00m to the right along the floor by applied force F_A at theta = 30 degree. The coefficient of K.E. is mu_k = 0.2 00. a) How much work is done by the applied force? b) How much work is done by the gravitational force on the box? c) How much work is done by the kinetic friction force? A 0.5 kg block initially is pushed against a spring with k = 250N/m, compressing it 0.06m. The block is then released from that position, and slides without friction up the curved track. a) Initially, how much energy (in Joules) is stored in the spring? b) When the block first leaves the spring, how fast is it going? c) What maximum height h above the starting point will the block reach (before sliding back down towards the spring)?

Explanation / Answer

7) F = umgCosQ

F = 0.2*12*9.81*Cos30 = 20.3897 N

W = F.d = 20.3897*3 = 61.17 J

b) By gravitational force = 0.., because displacement is in horizontal direction

c) W = 61.17 J

8) Energy = 0.5*250*0.06^2 = 0.45 J

b) 0.45 = 0.5*0.5*v^2

v = 1.34 m/s

c) mgh = 0.45

   h = 0.45 / 9.81*0.5

h = 0.092 m

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