Study Guides/Physics/A Cabin is Moved Up the Inclined Plane — Work and Force Analysis
Study Guide · Physics

A Cabin is Moved Up the Inclined Plane — Work, Force, and Energy

When a cabin is moved up an inclined plane, the applied force must overcome both the component of gravity along the incline (mg sinθ) and friction force (μmg cosθ). The work done is calculated as W = F × d, where d is the displacement along the incline. This is a classic mechanics problem involving work-energy theorem and Newton's laws on an incline.

Question (Click to Flip)

What force is needed to move a cabin up an inclined plane?

Answer

The force needed to move a cabin of mass m up an incline of angle θ with friction coefficient μ is: F = mg(sinθ + μcosθ). This accounts for the gravitational component along the incline (mg sinθ) and the friction force (μmg cosθ).

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Key Facts

Force to move a cabin up an incline: F = mg(sinθ + μcosθ).

Normal force on an inclined plane: N = mg cosθ.

Friction force on incline: f = μmg cosθ.

Work done = Force × displacement along incline = F × d.

Minimum work against gravity = mgh (height gained).

Work-energy theorem: Net work done = Change in kinetic energy.

On a frictionless incline, F = mg sinθ is the minimum force needed.

Forces Acting on a Cabin on an Inclined Plane

For a cabin of mass m on an incline of angle θ:

  1. Weight component along incline (opposing upward motion): mg sinθ
  2. Normal force perpendicular to incline: N = mg cosθ
  3. Friction force (opposing motion, acting downward along incline): f = μN = μmg cosθ
  4. Applied force (to move cabin upward): F = mg sinθ + μmg cosθ

Simplified: F = mg(sinθ + μcosθ)

Where:

  • m = mass of cabin
  • g = 9.8 m/s² (acceleration due to gravity)
  • θ = angle of incline
  • μ = coefficient of friction

Work Done Moving a Cabin Up an Inclined Plane

Work done by applied force: W = F × d = mg(sinθ + μcosθ) × d

Where d = distance moved along the incline

Relation to height: If the cabin rises by height h, h = d × sinθ, so d = h/sinθ

Minimum work done (without friction) = mgh (only gain in potential energy)

With friction: W = mgh + μmg cosθ × d

Energy balance:

  • Useful work = gain in PE = mgh
  • Wasted energy = work done against friction = μmgd cosθ
  • Efficiency = mgh / (mgh + μmgd cosθ) × 100%

Application: Work-Energy Theorem on Inclined Plane

If the cabin starts from rest and reaches velocity v after displacement d:

Net work = Change in KE (F - mg sinθ - f) × d = ½mv² - 0

If moving at constant velocity (a = 0): F = mg sinθ + μmg cosθ (net force = 0)

Special cases:

  • If θ = 0° (horizontal surface): F = μmg (only friction)
  • If θ = 90° (vertical): F = mg + friction at wall
  • Frictionless incline: F = mg sinθ

Questions and Answers

What force is needed to move a cabin up an inclined plane?+

The force needed to move a cabin of mass m up an incline of angle θ with friction coefficient μ is: F = mg(sinθ + μcosθ). This accounts for the gravitational component along the incline (mg sinθ) and the friction force (μmg cosθ).

How is work done calculated when a cabin moves up an inclined plane?+

Work done = Force × displacement along the incline = F × d = mg(sinθ + μcosθ) × d. If only the height h gained is known and friction is ignored, W = mgh.

What is the normal force on a cabin on an inclined plane?+

The normal force on a cabin on an inclined plane is N = mg cosθ, which is the component of the cabin's weight perpendicular to the incline surface.

What is the work-energy theorem and how does it apply to motion on an inclined plane?+

The work-energy theorem states that the net work done on an object equals the change in its kinetic energy: W_net = ΔKE = ½mv² − ½mu². On an inclined plane, the forces doing work include the applied force, gravity component along incline, and friction. At constant velocity, net work = 0, so the applied force exactly balances gravity and friction components.

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