A box is lifted with a pry bar, by slipping the bar under the box and lifting up on the bar. If the pry bar is 2m in length and it is grasped at the end, and the box is located at the opposite end, the fulcrum, with its center of gravity at a distance of 0.5 m from the fulcrum.
what is the size of the force required to lift the box if the box has a weight of 100N?
To determine the force required to lift the box using the pry bar, we can use the principle of moments.
The principle of moments states that the sum of the clockwise moments about any point is equal to the sum of the anticlockwise moments about the same point.
In this case, we can take moments about the fulcrum. The weight of the box creates a clockwise moment, while the force applied at the end of the pry bar creates an anticlockwise moment.
The equation for moments is given by:
Clockwise Moment = Anticlockwise Moment
The clockwise moment is the weight of the box multiplied by the distance of the center of gravity from the fulcrum:
Clockwise Moment = Weight of the box * Distance of center of gravity from fulcrum
The anticlockwise moment is the force applied multiplied by the length of the pry bar:
Anticlockwise Moment = Force * Length of the pry bar
Plugging in the given values:
Weight of the box = 100N
Distance of center of gravity from fulcrum = 0.5m
Length of the pry bar = 2m
The equation can be written as:
100N * 0.5m = Force * 2m
Simplifying the equation:
50Nm = 2m * Force
Dividing both sides of the equation by 2m:
Force = 50Nm / 2m
Therefore, the force required to lift the box using the pry bar is 25N.