Question icon
Grade 12Mechanics

a mass m rests on a frictionless horizontal table and is connected to rigid suppporets via 2 identical springs each of relaxed length lo and spring constant k.each spring is stretched to length l considerably larger than lo.horizontal displacement of m from its equilibrium posn is x and vertical is y.question is if at t=0 mass m is released from point x=y=A0 with 0 velocity,what are its x and y coordinates at any later time t?

Profile image of SHIVAM JAIN
13 Years agoGrade 12
Answers icon

1 Answer

Profile image of Askiitians Tutor Team
ApprovedApproved Tutor Answer11 Months ago

To analyze the motion of the mass m connected to two identical springs, we need to consider the forces acting on the mass and how they influence its position over time. Since the system is set up on a frictionless table, the only forces acting on the mass will be the restoring forces from the springs. Let's break this down step by step.

Understanding the System

Initially, the mass m is at the point (A0, A0) with zero velocity. When released, the springs will exert forces that will cause the mass to oscillate. The key points to consider are:

  • The springs are initially stretched, which means they have potential energy stored in them.
  • The mass will experience a restoring force that is proportional to its displacement from the equilibrium position.
  • Both horizontal (x) and vertical (y) motions will be influenced by the same spring forces.

Spring Force Calculation

The force exerted by a spring can be described by Hooke's Law, which states that the force F exerted by a spring is proportional to its displacement from the equilibrium position:

F = -k * x

For our mass m, we have two springs acting on it. If we denote the horizontal displacement from equilibrium as x and the vertical displacement as y, the forces in the x and y directions can be expressed as:

  • Fx = -k * x
  • Fy = -k * y

Setting Up the Equations of Motion

Using Newton's second law, we can write the equations of motion for the mass:

  • m * ax = -k * x
  • m * ay = -k * y

Where ax and ay are the accelerations in the x and y directions, respectively. This leads us to the following second-order differential equations:

  • ax = - (k/m) * x
  • ay = - (k/m) * y

Solving the Differential Equations

These equations are characteristic of simple harmonic motion. The general solution for each direction can be expressed as:

  • x(t) = Ax * cos(ωt + φ)
  • y(t) = Ay * cos(ωt + φ)

Where:

  • Ax and Ay are the amplitudes of motion in the x and y directions, respectively.
  • ω = √(k/m) is the angular frequency of the oscillation.
  • φ is the phase constant, which depends on the initial conditions.

Applying Initial Conditions

At time t = 0, we know that:

  • x(0) = A0
  • y(0) = A0
  • vx(0) = 0
  • vy(0) = 0

From these conditions, we can determine that:

  • Ax = A0
  • Ay = A0
  • φ = 0 (since the mass starts from maximum displacement with zero velocity)

Final Expressions for x and y

Substituting these values back into our equations gives us:

  • x(t) = A0 * cos(√(k/m) * t)
  • y(t) = A0 * cos(√(k/m) * t)

Thus, at any later time t, the coordinates of the mass m will be:

  • x(t) = A0 * cos(√(k/m) * t)
  • y(t) = A0 * cos(√(k/m) * t)

This demonstrates how the mass oscillates in both the x and y directions with the same frequency and amplitude, resulting in a circular motion in the x-y plane if you were to plot it. The system exhibits simple harmonic motion due to the restoring forces of the springs, and the coordinates can be easily calculated at any time t using the derived equations.