(a)
Clockwise and counter-clockwise torques acting on the board due to the four forces shown about an axis pointing out of the page at the 0−cm point.

Answer to Problem 101QAP
Clockwise torque= τclockwise=1.75Nm
Counter-clockwise torquey1 = 3 τcounter−clockwise=1.75Nm
Explanation of Solution
Given:
Formula used:
Torque can be interpreted as,
τ=Fr ( τ= Torque, F= Force, r= distance from rotational axis)
Calculation:
Consider the clockwise torque,
τclockwise=0.1kg*10ms−2*10*10−2m+50*10−3kg*10ms−2*50*10−2m+0.2kg*10ms−2*70*10−2m
τclockwise=(1+2.5+14)*10−1Nm
τclockwise=1.75Nm
Consider the vertical forces of the system,
Fpivot=(0.1kg+0.2kg+0.050kg)10ms−2
Fpivot=(0.350kg)10ms−2
Fpivot=3.5N
Consider the counter-clockwise torque,
τcounter−clockwise=3.5N*50*10−2m
τcounter−clockwise=1.75Nm
Conclusion:
Clockwise and counter-clockwise torques acting on the board due to the four forces shown about an axis pointing out of the page at the 0−cm point are;
τclockwise=1.75Nm
τcounter−clockwise=1.75Nm
(b)
Clockwise and counter-clockwise torques acting on the board due to the four forces shown about an axis pointing out of the page at the 50−cm point.

Answer to Problem 101QAP
Clockwise torque= τclockwise=0.4Nm
Counter-clockwise torque= τcounter−clockwise=0.4Nm
Explanation of Solution
Given:
Formula used:
Torque can be interpreted as,
τ=Fr ( τ= Torque, F= Force, r= distance from rotational axis)
Calculation:
Consider the clockwise torque,
τclockwise=0.2kg*10ms−2*20*10−2m
τclockwise=0.4Nm
Consider the counter-clockwise torque,
τcounter−clockwise=0.1kg*10ms−2*(50−10)*10−2m
τcounter−clockwise=0.4Nm
Conclusion:
Clockwise and counter-clockwise torques acting on the board due to the four forces shown about an axis pointing out of the page at the 50−cm point are;
τclockwise=0.4Nm
τcounter−clockwise=0.4Nm
(c)
Clockwise and counter-clockwise torques acting on the board due to the four forces shown about an axis pointing out of the page at the 100−cm point.

Answer to Problem 101QAP
Clockwise torque= τclockwise=1.75Nm
Counter-clockwise torque= τcounter−clockwise=1.75Nm
Explanation of Solution
Given:
Formula used:
Torque can be interpreted as,
τ=Fr ( τ= Torque, F= Force, r= distance from rotational axis)
Calculation:
Consider the clockwise torque,
τclockwise=Fpivot*50*10−2m
τclockwise=0.35N*50*10−2m
τclockwise=1.75Nm
Consider the counter-clockwise torque,
τcounter−clockwise=0.2kg*10ms−2*(100−70)*10−2m+0.050kg*10ms−2*(100−50)*10−2m+0.100kg*10ms−2*(100−10)*10−2m
τcounter−clockwise=(0.6Nm+0.25Nm+0.9Nm)
τcounter−clockwise=1.75Nm
Conclusion:
Clockwise and counter-clockwise torques acting on the board due to the four forces shown about an axis pointing out of the page at the 100−cm point are;
τclockwise=1.75Nm
τcounter−clockwise=1.75Nm
(d)
Verify the stability of the stick after the two masses have been added.

Explanation of Solution
Given:
Formula used:
Torque can be interpreted as,
τ=Fr ( τ= Torque, F= Force, r= distance from rotational axis)
Calculation:
Consider the conclusions of (a),(b),(c) parts,
According to conclusion (a),
τclockwise=1.75Nm
τcounter−clockwise=1.75Nm
So,
τclockwise=τcounter−clockwise...(1)
According to conclusion (b),
τclockwise=0.4Nm
τcounter−clockwise=0.4Nm
So,
τclockwise=τcounter−clockwise...(2)
According to conclusion (c),
τclockwise=1.75Nm
τcounter−clockwise=1.75Nm
So,
τclockwise=τcounter−clockwise...(3)
Conclusion:
According to (1),(2),(3) expressions,
Stability of the stick after the two masses have been added is still strong. In other words system has stabilized.
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Chapter 8 Solutions
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