Math Problem Statement

A block of mass m = 15.0 kg moves up an incline with constant velocity while being pushed by a force F. The kinetic coefficient of friction between the block and the floor is μk = 0.375, and the incline makes an angle of θ = 30.0° with respect to the horizontal. What is the magnitude of F?

Solution

The problem asks to find the magnitude of the force FF required to push a block of mass m=15.0kgm = 15.0 \, \text{kg} up an incline at a constant velocity, where the incline has an angle θ=30\theta = 30^\circ, and the coefficient of kinetic friction is μk=0.375\mu_k = 0.375.

Breakdown of Forces:

  1. Gravitational force Fg=mgF_g = mg, where g9.8m/s2g \approx 9.8 \, \text{m/s}^2.

    • The component of gravity parallel to the incline is Fgsinθ=mgsinθF_g \sin\theta = mg\sin\theta.
    • The component of gravity perpendicular to the incline is Fgcosθ=mgcosθF_g \cos\theta = mg\cos\theta.
  2. Normal force NN: Since there is no acceleration perpendicular to the incline, the normal force is balanced by the perpendicular component of gravity: N=mgcosθN = mg \cos\theta

  3. Frictional force FfF_f: The kinetic friction opposes the motion and is given by Ff=μkNF_f = \mu_k N. Substituting NN: Ff=μkmgcosθF_f = \mu_k mg \cos\theta

  4. Total force required FF: To maintain constant velocity, the applied force FF must balance both the force due to gravity (parallel to the incline) and the frictional force. The equation for the required force is: F=Fgsinθ+FfF = F_g \sin\theta + F_f Substituting the expressions for FgF_g and FfF_f: F=mgsinθ+μkmgcosθF = mg \sin\theta + \mu_k mg \cos\theta

Now, let’s calculate the magnitude of FF.The magnitude of the force FF required to push the block up the incline at a constant velocity is approximately 121.24N121.24 \, \text{N}.

Would you like further details on any part of the solution, or have any specific questions?

Here are five related questions to expand your understanding:

  1. How would the force change if the incline angle increased?
  2. What happens to the frictional force if the surface becomes smoother (lower μk\mu_k)?
  3. How would the required force change if the mass of the block doubled?
  4. What would happen to the force if the block was moving down the incline at a constant velocity?
  5. How does the constant velocity assumption simplify the problem?

Tip: In problems involving inclines, always break forces into components parallel and perpendicular to the incline.

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Math Problem Analysis

Mathematical Concepts

Newton's Laws
Inclined Plane Physics
Friction

Formulas

Gravitational force: Fg = mg
Parallel component of gravity: Fg sinθ
Perpendicular component of gravity: Fg cosθ
Normal force: N = mg cosθ
Frictional force: Ff = μk N
Force balance: F = Fg sinθ + Ff

Theorems

Newton's Second Law
Frictional Force Equation

Suitable Grade Level

Grades 10-12