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Ch 05: Applying Newton's Laws
Young & Freedman Calc - University Physics 14th Edition
Young & Freedman Calc14th EditionUniversity PhysicsISBN: 9780321973610당신이 사용하는 게 아니라요?교과서 변경
5장, 문제 37a

Two crates connected by a rope lie on a horizontal surface (Fig. E5.375.37). Crate A has mass mAm_A, and crate B has mass mBm_B. The coefficient of kinetic friction between each crate and the surface is μkμ_k. The crates are pulled to the right at constant velocity by a horizontal force FF. Draw one or more free-body diagrams to calculate the following in terms of mAm_A, mBm_B, and μkμ_k: the magnitude of FF.
Illustration of crates A and B on a surface, connected by a rope, with force F acting to the right.

검증된 단계별 안내
1
Step 1: Begin by analyzing the forces acting on each crate. For crate A, the forces include the tension in the rope (T), the kinetic friction force opposing motion (f_kA = μk * mA * g), and the normal force (N_A = mA * g). For crate B, the forces include the applied force (F), the tension in the rope (T), the kinetic friction force opposing motion (f_kB = μk * mB * g), and the normal force (N_B = mB * g).
Step 2: Since the crates are moving at constant velocity, the net force on the system is zero. This means the applied force F must balance the total frictional forces acting on both crates. Write the equation for the total frictional force: f_total = f_kA + f_kB = μk * mA * g + μk * mB * g.
Step 3: The tension in the rope (T) connecting the crates is internal to the system and does not affect the calculation of F. Therefore, the applied force F must equal the total frictional force to maintain constant velocity: F = f_total = μk * mA * g + μk * mB * g.
Step 4: Substitute the expressions for the frictional forces into the equation for F. This gives: F = μk * g * (mA + mB).
Step 5: Conclude that the magnitude of the applied force F required to pull the crates at constant velocity is determined by the combined mass of the crates, the coefficient of kinetic friction, and the acceleration due to gravity. The final expression for F is: F = μk * g * (mA + mB).

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.
영상 길이:
11m
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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Free-Body Diagram

A free-body diagram is a graphical representation used to visualize the forces acting on an object. In this scenario, each crate (A and B) will have its own free-body diagram showing the applied force, gravitational force, normal force, and frictional force. This helps in analyzing the net forces and understanding how they affect the motion of the crates.
추천 영상:
08:42
Free-Body Diagrams

Friction

Friction is the resistive force that opposes the motion of two surfaces in contact. The coefficient of kinetic friction (μ_k) quantifies this resistance when the surfaces are sliding against each other. In this problem, friction acts on both crates, affecting the total force required to maintain constant velocity, which is crucial for calculating the applied force F.
추천 영상:
08:11
Static Friction & Equilibrium

Newton's Second Law

Newton's Second Law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass (F = ma). In this case, since the crates are moving at constant velocity, the net force is zero, meaning the applied force F must balance the total frictional forces acting on both crates. This principle is essential for determining the magnitude of F.
추천 영상:
06:54
Intro to Forces & Newton's Second Law
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