/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 107 The drawing shows Robin Hood (ma... [FREE SOLUTION] | 91Ó°ÊÓ

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The drawing shows Robin Hood (mass \(=77.0 \mathrm{kg}\) ) about to escape from a dangerous situation. With one hand, he is gripping the rope that holds up a chandelier (mass \(=195 \mathrm{kg}\) ). When he cuts the rope where it is tied to the floor, the chandelier will fall, and he will be pulled up toward a balcony above. Ignore the friction between the rope and the beams over which it slides, and find (a) the acceleration with which Robin is pulled upward and (b) the tension in the rope while Robin escapes.

Short Answer

Expert verified
(a) Acceleration is \(4.01 \mathrm{m/s^2}\). (b) Tension in the rope is \(1130.85 \mathrm{N}\).

Step by step solution

01

Identify Forces Acting on Both Objects

Start by identifying the forces acting on Robin Hood and the chandelier. For Robin Hood, these forces are the tension in the rope (upward) and his weight (downward), given by \(mg\), where \(m = 77.0\, \mathrm{kg}\). For the chandelier, the forces are the tension in the rope (upward) and its weight (downward), given by \(Mg\), where \(M = 195\, \mathrm{kg}\).
02

Apply Newton's Second Law to Robin Hood

Use Newton's second law for Robin Hood: \( T - mg = ma \) where \( T \) is the tension, \( m = 77.0 \mathrm{kg} \) is Robin's mass, and \( a \) is the acceleration. This gives us the equation for Robin Hood: \( T = m(a + g) \).
03

Apply Newton's Second Law to the Chandelier

Similarly, apply Newton's second law to the chandelier: \( Mg - T = Ma \) where \( M = 195 \mathrm{kg} \) is the mass of the chandelier. This gives us the equation for the chandelier: \( T = Mg - Ma \).
04

Equate Tensions to Solve for Acceleration

Set the equations for the tensions equal to solve for the acceleration \(a\): \( m(a + g) = Mg - Ma \). Rearrange the equation to solve for \(a\): \( a = \frac{M - m}{M + m}g \). Substitute \( g = 9.8 \mathrm{m/s^2} \), \( M = 195 \mathrm{kg} \), and \( m = 77 \mathrm{kg} \) to find \( a \).
05

Calculate the Acceleration

Substitute the given values into the expression: \( a = \frac{195 - 77}{195 + 77} \times 9.8 \approx 4.01 \mathrm{m/s^2} \). This is the acceleration with which Robin is pulled upward.
06

Calculate the Tension in the Rope

Use the expression for tension from the chandelier: \( T = Mg - Ma \). Substitute \( M = 195 \mathrm{kg} \), \( g = 9.8 \mathrm{m/s^2} \), and \( a = 4.01 \mathrm{m/s^2} \) to find \( T \). So, \( T = 195 \times 9.8 - 195 \times 4.01 = 1130.85 \mathrm{N} \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Tension in the Rope
The concept of tension in the rope is crucial when solving problems involving dynamics and forces, as seen in Robin Hood's challenge with the chandelier. When a rope or cable is used to lift or pull something, the tension refers to the force that is transmitted through the rope. This force is responsible for overcoming the weight of the object being lifted.

In Robin Hood's scenario, the rope tension plays a dual role: it pulls him upward while also supporting the chandelier as it begins its descent. The tension can be calculated using Newton's Second Law, by setting up equations for both Robin Hood and the chandelier:

  • For Robin Hood, his weight acts downward, and the tension forces him upward. The equation is given by: \[ T = m(a + g) \]where \( m = 77.0 \mathrm{kg} \) is Robin's mass, \( g = 9.8 \mathrm{m/s^2} \) is the acceleration due to gravity, and \( a \) is the upward acceleration.
  • For the chandelier, the tension must overcome its weight. The equation becomes:\[ T = Mg - Ma \]where \( M = 195 \mathrm{kg} \) is the chandelier's mass.
By equating these tensions from the respective equations, one can solve for the desired quantities of tension or acceleration as needed.
Acceleration Due to Gravity
Acceleration due to gravity, represented by the symbol \( g \), is a fundamental force acting on all objects near the surface of the Earth. It's a crucial component in the calculations involving forces and motion. In scenarios like Robin Hood's, this constant helps determine how fast objects like him or the chandelier will accelerate when subjected to other forces.

On Earth, this value is approximately \( 9.8 \, \mathrm{m/s^2} \). This is important because it's a constant factor in the equations used to solve for other variables like tension and upward acceleration. In the formula for Robin's upward acceleration, both his mass and the chandelier's mass are influenced by \( g \).
  • In the equation for Robin Hood, the upward force we need to overcome (besides tension) is his weight: \( m \times g \).
  • For the chandelier, the force pulling it down is its weight: \( M \times g \).
Understanding \( g \) helps us realize that it's the same gravity causing objects to fall, which must be compensated by upward forces like tension, allowing Robin to ascend to safety.
Forces and Motion Analysis
Forces and motion analysis is a fundamental discipline in physics that allows us to predict how objects will behave when subjected to various forces. When analyzing the forces in the case of Robin Hood and the chandelier, we apply Newton's Second Law, which states that \[ \vec{F} = m \cdot \vec{a} \]. This principle helps us connect the sum of forces to the motion of any object.

In Robin Hood's escape, the forces acting on him are his weight and the tension from the rope, while on the chandelier, its weight subtracts the tension from the rope. By writing down the respective equations and solving for unknowns, we can understand how both Robin and the chandelier will move:
  • The upward motion of Robin is dictated by the net forces acting on him – primarily the balance between rope tension and gravitational pull.
  • The chandelier's fall and the associated rope tension set the stage for Robin's rapid ascent.
By systematically breaking down these forces into their components and applying Newton’s Law, we gain a deeper comprehension of the interconnected nature of motion and force.

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