Find the magnitude of the torque

In summary, the magnitude of the torque about P is 136 lb. The torque can be calculated using the vector equation t = r x F, where r is the distance at which the force is acting and F is the applied force. The resulting torque can be expressed as a vector and its magnitude can be found by taking the square root of the dot product of the torque vector with itself.
  • #1
jonnejon
27
0

Homework Statement


Find the magnitude of the torque about P if a 68 lb force is applied as shown. Give your answer correct to the nearest integer.
12-4-40.gif

Homework Equations


t=r X F

The Attempt at a Solution


t = (4)(68)(sin30)
= 136
 
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  • #2


Don't you want to consider the distance at which it is acting is 4*√2 ?

At the point of interaction then the ⊥ component of F looks to me like F*Cos15°
 
  • #3


jonnejon said:

Homework Statement


Find the magnitude of the torque about P if a 68 lb force is applied as shown. Give your answer correct to the nearest integer.
12-4-40.gif



Homework Equations


t=r X F


The Attempt at a Solution


t = (4)(68)(sin30)
= 136


You wrote what must have been intended to be a vector equation for the torque, t = r x F, because the cross product only makes sense if t, r, and F are all expressed as vectors. But then you proceeded to do a scalar calculation. Why not make your torque calculation in vector form using the determinant expression for the cross product and giving the resulting torque as a vector? Then if you need the magnitude of that vector, dot it with itself and take the square root of the result.
 

Related to Find the magnitude of the torque

1. What is torque and how is it measured?

Torque is a measure of the force that causes an object to rotate. It is typically measured in Newton-meters (Nm) or foot-pounds (ft-lb). It is calculated by multiplying the force applied to an object by the distance from the pivot point where the force is applied.

2. How is torque different from force?

While force is a measure of the push or pull on an object, torque is a measure of the rotational force applied to an object. Force is typically measured in Newtons (N) or pounds (lbs), while torque is measured in Newton-meters (Nm) or foot-pounds (ft-lb).

3. What factors affect the magnitude of torque?

The magnitude of torque depends on the amount of force applied, the distance from the pivot point where the force is applied, and the angle between the force and the lever arm. The longer the lever arm, the greater the torque will be for a given force.

4. How do you calculate the magnitude of torque?

To calculate the magnitude of torque, you need to know the force applied, the distance from the pivot point, and the angle between the force and the lever arm. The formula for torque is: torque = force x distance x sin(angle).

5. Can torque be negative?

Yes, torque can be negative. A negative torque indicates that the force is causing the object to rotate in the opposite direction of a positive torque. This can happen when the force is applied in the opposite direction of the lever arm, or when the angle between the force and the lever arm is greater than 90 degrees.

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