The figure below shows a standard man intending to do reverse curls in a gym (standing up with Tension up, weight of arm down and force down). He holds his arms straight, using an overhand grip to hold the bar. If the mass of the bar is given as 146 kg, what is the tension in each of his shoulders? Consider the weight of the arm and the weight of the bar.
Another "figure below" question. Please read my comments to "Sam"
To find the tension in each of the man's shoulders, we need to consider the forces acting on his arms. Let's break down the problem step by step:
1. Identify the forces acting on the man's arms:
- Tension force: The force exerted by the man's muscles to curl the weight.
- Weight of the bar: Due to gravity, the bar exerts a downward force.
- Weight of the arms: Similar to the bar, the arms also have a weight that exerts a downward force.
2. Set up the free-body diagram:
- Draw a diagram of the man's arms and label the forces acting on them.
- The upward tension force and the downward forces of the weight of the bar and the arms should be included.
3. Apply Newton's Second Law:
- Newton's Second Law states that the net force acting on an object is equal to the mass of the object multiplied by its acceleration.
- In this case, since the man's arms are not accelerating (assuming he is holding the position), the net force is zero.
- The net force is the vector sum of all the forces acting on the arms.
4. Equate the forces:
- The tension force in the arms should be equal to the sum of the weights acting downward.
Tension force = Weight of the bar + Weight of the arms
5. Calculate the tension in each shoulder:
- The weight of the bar is given as 146 kg.
- The weight of the arms can be calculated using the mass of the arms and the acceleration due to gravity (9.8 m/s^2).
Weight of the arms = mass of the arms * acceleration due to gravity
Once you have both values, add them together to find the tension in each shoulder.
It's important to note that this explanation assumes that there are no external forces acting on the man's arms, such as friction or air resistance. Additionally, the size and shape of the bar, as well as the position and strength of the man, can also affect the tension in each shoulder.