Free body diagram Homework Problem

In summary, the problem involves a bear trying to reach a picnic basket at the end of a 6m beam with a mass of 40kg and a 10kg basket. The bear weighs 150kg and is 1m from the wall. The wire is at a 60 degree angle above the horizontal and can support a tension of 1500N. The problem asks for the tension in the wire, the horizontal and vertical components of the force exerted by the wall, the maximum distance the bear can walk before the wire snaps, and the moment of inertia for the bear, basket, and beam. It also asks for the total moment of inertia and the angular and tangential acceleration if the wire snaps. To solve the
  • #1
Physically Impaired
9
0
Can someone please help with this problem. I'm lost!

1. A 150 kg bear walks out onto a beam as illustrated in Fig P8.20 trying to get to a picnic
basket with mass 10kg. The beam is 6m long and has mass 40kg (you can consider its
weight to be concentrated at a point 3m from the wall.
(a) When the bear is 1m from the wall, how much tension will be in the wire? (The wire
is at an angle of 60o above the horizontal, directed toward the wall.)
(b) What is the horizontal component of the force of the wall on the beam at this point?
(c) What is the vertical component of the force of the wall on the beam at this point?
(d) If the wire can support a tension of 1500N, what is the maximum distance from the
wall the bear can walk.
(e) What is the moment of inertia of the bear at this point assuming its moment of inertia
is mx2, where m is the bear’s mass and x is the distance from the wall.
(f) What is the moment of inertia of the basket, again assuming its moment of inertia is
ml2 where m is the basket’s mass and l is the length of the beam.
(g) What is the moment of inertia of the beam assuming its moment of inertia is 1
3
ml2,
where m is the mass of the beam, and l is the length of the beam.
(h) What is the total moment of inertia (add the last three answers).
(i) If the wire was to snap with the bear at this point, what would be the angular acceleration
of the beam, bear and basket immediately after the wire snaps (assume they all
accelerate as one object with the moment of inertia as given above).
(j) What would be the bear’s tangential acceleration?
 
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  • #2
This problem is quite direct. All you need to do is to draw a free body diagram. Remember that when dealing with static problems, FBD is essential to solve them.

Since you didn't mention about the location of the basket, I will just assume that it is at the end of the beam. Assign A as the contact point of the beam with the wall. Using [tex]\sum{M_A}=0[/tex], you can find out the tension of the rope. After getting the tension of the rope, the rest of the question can be solved easily.
 
  • #3


First, let's draw a free body diagram for the problem:

1. Bear:
- Weight (150kg) pointing downwards
- Tension in the wire (unknown) pointing upwards and to the left at a 60 degree angle
- Normal force from the beam (unknown) pointing upwards and to the right

2. Picnic basket:
- Weight (10kg) pointing downwards
- Tension in the wire (unknown) pointing upwards and to the left at a 60 degree angle

3. Beam:
- Weight (40kg) concentrated at a point 3m from the wall, pointing downwards
- Tension in the wire (unknown) pointing upwards and to the left at a 60 degree angle
- Normal force from the wall (unknown) pointing upwards and to the right

Now, let's solve for the unknowns in each part of the problem:

(a) Using the free body diagram for the bear, we can set up the following equation:
ΣFy = 0
N - 150kg(9.8m/s²)sin60° = 0
N = 735N
Therefore, the tension in the wire is 735N.

(b) Using the free body diagram for the beam, we can set up the following equation:
ΣFx = 0
Fx = 0
Therefore, the horizontal component of the force of the wall on the beam is 0N.

(c) Using the free body diagram for the beam, we can set up the following equation:
ΣFy = 0
N + Tsin60° - 40kg(9.8m/s²) = 0
N = 294N
Therefore, the vertical component of the force of the wall on the beam is 294N.

(d) To find the maximum distance from the wall the bear can walk, we can set up the following equation using the free body diagram for the bear:
ΣFx = 0
Tcos60° = 150kg(9.8m/s²)
T = 1470N
Therefore, the maximum distance from the wall the bear can walk is 1470N/(150kg(9.8m/s²)) = 1.02m.

(e) The moment of inertia of the bear can be calculated using the formula I = mx². Plugging in the values, we get:
I = (150kg)(
 

FAQ: Free body diagram Homework Problem

What is a free body diagram?

A free body diagram is a visual representation of the forces acting on an object. It is often used in physics and engineering to analyze the motion or equilibrium of an object.

How do I draw a free body diagram?

To draw a free body diagram, you will need to identify all the external forces acting on the object, including weight, normal force, friction, and any other applied forces. Then, draw a simple diagram of the object and use arrows to represent the direction and magnitude of each force.

Why is it important to use free body diagrams?

Free body diagrams are important because they help us understand the forces acting on an object and how they affect its motion or equilibrium. They also allow us to identify any missing or incorrect information in a problem and guide us in finding a solution.

What are some common mistakes when drawing free body diagrams?

Some common mistakes when drawing free body diagrams include forgetting to label the forces, drawing the forces at incorrect angles, and not considering all the external forces acting on the object. It is important to double-check your diagram to ensure accuracy.

Can I use a free body diagram for objects in motion?

Yes, free body diagrams can be used for objects in motion as well as objects in equilibrium. In motion, the sum of all the forces must equal the mass of the object multiplied by its acceleration, as described by Newton's Second Law.

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