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Ch 10: Interactions and Potential Energy
Knight Calc - Physics for Scientists and Engineers 5th Edition
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Not the one you use?Change textbook
Chapter 10, Problem 53b

The ice cube is replaced by a 50 g plastic cube whose coefficient of kinetic friction is 0.20. How far will the plastic cube travel up the slope? Use work and energy.

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Identify the forces acting on the plastic cube: The forces include gravity, the normal force, and the kinetic friction force. The work-energy principle will be used to solve the problem.
Write the expression for the initial kinetic energy of the cube: \( KE_{initial} = \frac{1}{2} m v^2 \), where \( m \) is the mass of the cube and \( v \) is its initial velocity.
Determine the work done by friction: The work done by friction is \( W_{friction} = -f_k d \), where \( f_k = \mu_k N \) is the kinetic friction force, \( \mu_k \) is the coefficient of kinetic friction, \( N = m g \cos \theta \) is the normal force, and \( d \) is the distance traveled up the slope.
Write the expression for the change in gravitational potential energy: \( \Delta U = m g h \), where \( h = d \sin \theta \) is the height gained by the cube as it moves up the slope.
Apply the work-energy principle: \( KE_{initial} + W_{friction} = \Delta U \). Substitute the expressions for \( KE_{initial} \), \( W_{friction} \), and \( \Delta U \) into this equation, and solve for \( d \), the distance the cube travels up the slope.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Kinetic Friction

Kinetic friction is the force that opposes the motion of two surfaces sliding past each other. It is quantified by the coefficient of kinetic friction, which is a dimensionless value representing the ratio of the frictional force to the normal force. In this scenario, the coefficient of kinetic friction (0.20) indicates how much frictional force will act against the motion of the plastic cube as it moves up the slope.
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Work-Energy Principle

The work-energy principle states that the work done on an object is equal to the change in its kinetic energy. In this context, as the plastic cube moves up the slope, work is done against both gravity and friction. This principle allows us to calculate how far the cube will travel by equating the work done by the applied forces to the energy changes experienced by the cube.
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Potential Energy

Potential energy is the energy stored in an object due to its position in a gravitational field. For an object on an incline, the potential energy increases as it rises to a higher elevation. In this problem, the change in potential energy as the plastic cube moves up the slope must be considered, as it will affect how far the cube can travel before coming to a stop due to the opposing forces of gravity and friction.
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Related Practice
Textbook Question

A sled starts from rest at the top of the frictionless, hemispherical, snow-covered hill shown in FIGURE P10.56. a. Find an expression for the sled's speed when it is at angle ϕ .

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Textbook Question

A freight company uses a compressed spring to shoot 2.0 kg packages up a 1.0-m-high frictionless ramp into a truck, as FIGURE P10.52 shows. The spring constant is 500 N/m and the spring is compressed 30 cm. What is the speed of the package when it reaches the truck?

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Textbook Question

The spring shown in FIGURE P10.54 is compressed 50 cm and used to launch a 100 kg physics student. The track is frictionless until it starts up the incline. The student's coefficient of kinetic friction on the 30° incline is 0.15. What is the student's speed just after losing contact with the spring?

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Textbook Question

Two blocks with masses mA and mB are connected by a massless string over a massless, frictionless pulley. Block B, which is more massive than block A, is released from height h and falls. Write an expression for the speed of the blocks just as block B reaches the ground.

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Textbook Question

FIGURE 10.23 showed the potential-energy curve for the O2 molecule. Consider a molecule with the energy E1 shown in the figure. a. What is the maximum speed of an oxygen atom as it oscillates back and forth? Don't forget that the kinetic energy is the total kinetic energy of the system. The mass of an oxygen atom is 16 u, where 1u=1 atomic mass unit =1.66×10−27 kg .

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Textbook Question

Two blocks with masses mA and mB are connected by a massless string over a massless, frictionless pulley. Block B, which is more massive than block A, is released from height h and falls. A 1.0 kg block and a 2.0 kg block are connected by a massless string over a massless, frictionless pulley. The impact speed of the heavier block, after falling, is 1.8 m/s. From how high did it fall?

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