1) A block is on a frictionless horizontal table, on earth. This block accelerat

Question

1) A block is on a frictionless horizontal table, on earth. This block accelerates at 1.9 m/s2 when a 90 N horizontal force is applied to it. The block and table are then set up on the moon where the acceleration due to gravity is 1.62 m/s2. What is the weight of the block on the moon?

48 N B) 39 N C) 77 N D) 67 N E) 58 N

In a shuffleboard game, the puck slides a total of 12 m before coming to rest. If the coefficient of kinetic friction between the puck and the horizontal board is 0.28, what was the initial speed of the puck?

8.1 m/s B) 7.3 m/s C) 29.0 m/s D) 6.5 m/s

Explanation / Answer

from F = m*a..

mass m = F/a = (90)/1.9= 47.4 kg

weight W = m*g = (47.4*1.62) = 76.788 N

so the answer is C) 77 N

2) work done by froctional force = change in mechanical energy

W = 0.5*m*v^2..

mu_k*m*g*S = 0.5*m*v^2..
0.28*m*9.81*12 = 0.5*m*v^2...

m cancels

initial speed is v = sqrt(0.28*9.81*12/0.5) = 8.1 m/s
so the answer is A) 8.1 m/s

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