A ladder, length L, with mass M, leans against a frictionless wall at an angle o
ID: 1288827 • Letter: A
Question
A ladder, length L, with mass M, leans against a frictionless wall at an angle of ? = 70 as shown.
1)
If the ladder is in static equilibrium,
The net force is zero but the net torque is not.
The net torque is zero but the net force is not.
The net force and net torque are both zero.
Neither net force nor net torque is zero.
2)
Which of these free body diagrams best represents the forces on the ladder?
3)
At which of the following locations can we put the rotation axis we use when calculating torques?
Only at the center of the ladder.
Only at the bottom left end of the ladder.
Only at the top right end of the ladder.
We can choose any of these locations for the rotation axis.
4)
For the rest of these problems, we're using the top right end of the ladder as our pivot point. What is the magnitude of the torque from the force of gravity, around this point?
L*Mg*sin(?)
L*Mg*cos(?)
(L/2)*Mg*sin(?)
(L/2)*Mg*cos(?)
5)
To find the torque from the normal force from the ground, we need first find the force of the normal force from the ground. What is the normal force on the ladder from the ground?
Mg
Mg/2
(Mg/2)*sin(?)
(Mg/2)*cos(?)
6)
What is the magnitude of the torque from the normal force from the ground?
L*Nground*sin(?)
L*Nground*cos(?)
(L/2)*Nground*sin(?)
(L/2)*Nground*cos(?)
7)
What must be the magnitude of the torque from the friction on the ground?
|?friction| = |?gravity|+ |?normal|
|?friction| = |?normal| - |?gravity|
8)
If the angle of the ladder were decreased to 50, the required friction force to keep it in place would
increase.
decrease.
stay the same.
9)
Assume we've moved the ladder to an angle where the friction can no longer hold it in place and it starts to slip. The ladder is now experiencing
a net force but no net torque.
a net torque but no net force.
both a net force and a net torque.
neither a net force nor a net torque.
ladderd 3) At which of the following locations can we put the rotation axis we use when calculating torques? Only at the center of the ladder. Only at the bottom left end of the ladder. Only at the top right end of the ladder. We can choose any of these locations for the rotation axis. 4) For the rest of these problems, we're using the top right end of the ladder as our pivot point. What is the magnitude of the torque from the force of gravity, around this point? L*Mg*sin(?) L*Mg*cos(?) (L/2)*Mg*sin(?) (L/2)*Mg*cos(?) 5) To find the torque from the normal force from the ground, we need first find the force of the normal force from the ground. What is the normal force on the ladder from the ground? Mg Mg/2 (Mg/2)*sin(?) (Mg/2)*cos(?) 6) What is the magnitude of the torque from the normal force from the ground? L*Nground*sin(?) L*Nground*cos(?) (L/2)*Nground*sin(?) (L/2)*Nground*cos(?) 7) What must be the magnitude of the torque from the friction on the ground? |?friction| = |?gravity|+ |?normal| |?friction| = |?normal| - |?gravity| 8) If the angle of the ladder were decreased to 50½, the required friction force to keep it in place would increase. decrease. stay the same. 9) Assume we've moved the ladder to an angle where the friction can no longer hold it in place and it starts to slip. The ladder is now experiencing a net force but no net torque. a net torque but no net force. both a net force and a net torque. neither a net force nor a net torque. ladderc ladderb laddera ladder A ladder, length L, with mass M, leans against a frictionless wall at an angle of ? = 70½ as shown. 1) If the ladder is in static equilibrium, The net force is zero but the net torque is not. The net torque is zero but the net force is not. The net force and net torque are both zero. Neither net force nor net torque is zero. 2) Which of these free body diagrams best represents the forces on the ladder?Explanation / Answer
1) The net force and net torque are both zero.
2) third one
3) We can choose any of these locations for the rotation axis.
4)(L/2)*Mg*cos(?)
5)Mg
6)L*Nground*cos(?)
7)|?friction| = |?normal| - |?gravity|
8)increase
9)both a net force and a net torque.
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