Horizontal force on a horizontal bar

In summary, the conversation discusses the calculation of tension in a rope using torque and force balance equations. The symbol "T" represents tension in the rope and is not to be confused with the horizontal force of the wall acting on the bar. The torque balance equation alone cannot give this information, as force balance equations are also needed. The acceleration of gravity is also necessary to consider in the calculations. The final equation for tension is T=m/sinθ, where "m" represents the mass of the object and θ is the angle of the rope.
  • #1
marjine
10
1
Homework Statement
A uniform horizontal bar of mass m and
length L = 1.59 m is held by a frictionless
pin at a wall. The opposite end of the strut is
supported by a cord with tension T at an angle θ. A block of mass 2 m is hung from thebar at a distance of 3/4 L from the pin. If the mass of the bar is mass m = 1.52 kg, find the magnitude of the horizontal component of the force of the wall acting on the bar
if the string makes an angle of 39.7◦ with the
horizontal.
The acceleration of gravity is 9.8 m/s
Answer in units of N.
Relevant Equations
Tnet = sum Ti
T=rFsinθ
T=Ia
Tnet = 0 = Tcord-Twall-Tmass
TLsinθ-2m(3/4L)-m(1/2)L
TLsinθ= -(3/2)mL-(1/2)mL
T=m/sinθ
T= (1.52)/sin(39.7) = 2.38N
 

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  • #2
If I am not mistaken, the symbol ##T## stands for the tension in the rope. That is not the horizontal force of the wall acting on the bar. The torque balance equation cannot give you that. You also need the force balance equations. Also, you omitted the acceleration of gravity ##g## from the weights.
 
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  • #3
marjine said:
Tnet = 0 = Tcord-Twall-Tmass
TLsinθ-2m(3/4L)-m(1/2)L
=0, but that does not lead to:
marjine said:
TLsinθ= -(3/2)mL-(1/2)mL
Then you seem to have read that as +(3/2)mL-(1/2)mL to arrive at
marjine said:
T=m/sinθ
Also, your overuse of "T" is confusing. You have used it, as given, for the tension in the rope, as a base for subscripts for other forces (F would have been clearer) and for torque (try τ).
 
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FAQ: Horizontal force on a horizontal bar

What is a horizontal force?

A horizontal force is a force that acts parallel to the horizontal surface on which an object rests. It can cause an object to move along the horizontal plane.

How do you calculate the horizontal force on a horizontal bar?

The horizontal force on a horizontal bar can be calculated using Newton's second law, F = ma, where F is the force, m is the mass of the object, and a is the acceleration. Additionally, if the bar is in equilibrium, the sum of all horizontal forces acting on it must be zero.

What factors affect the horizontal force on a horizontal bar?

Several factors can affect the horizontal force on a horizontal bar, including the mass of the bar, the coefficient of friction between the bar and the surface, any applied loads, and the angle of applied forces.

How does friction influence the horizontal force on a horizontal bar?

Friction opposes the motion of the bar and must be overcome by any applied horizontal force. The frictional force can be calculated using the formula F_friction = μN, where μ is the coefficient of friction and N is the normal force.

Can a horizontal force cause a horizontal bar to rotate?

Yes, a horizontal force can cause a horizontal bar to rotate if it is applied at a point that is not along the bar's center of mass. This creates a torque, which can induce rotational motion.

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