net torque question

[ssiding]

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A rectangle book weighing 20N with sides of 10cm and 20cm is placed on a horizontal table. Using each of your hands, you exert forces of 10N each in opposite directions at opposite corners, such that you are pushing parallel to the shorter side in each case. What net torque are ou providing to the book?

A. 0 N-m
B. 0.5 N-M
C. 1 N-m
D. 2 N-m

 

[TieuBachHo]

Torgue = r F sin(angle of F and r)

Use trig. to find r = 5 x squr(5) cm ... sine = 2/squr(5) ... So Torgue = 100 N.cm = 1 N.m ... Net torque = 2 x torques = 2 N.m ... So answer is D ... double check your with ur answer. I think they bluff you with the weigh of the book since it's rested on the table. This problem is straight forward.