
Concept explainers
A small 0.65-kg box is launched from rest by a horizontal spring as shown in Figure P9.50. The block slides on a track down a hill and comes to rest at a distance d from the base of the hill. Kinetic friction between the box and the track is negligible on the hill, but the coefficient of kinetic friction between the box and the horizontal parts of track is 0.35. The spring has a spring constant of 34.5 N/m, and is compressed 30.0 cm with the box attached. The block remains on the track at all times.
a. What would you include in the system? Explain your choice.
b. Calculate d.
(a)

The items included in the system and explain the choice.
Answer to Problem 50PQ
The items included are the box and the tracks surface because the kinetic friction increases the thermal energies and included this thermal energy internal to the system.
Explanation of Solution
In order to keep all the thermal energy into the system, it is better to include both the box and the tracks surface so that it will increase the kinetic friction which leads to the increase in the thermal energies and including both keeps all of this thermal energy internal to the system.
If Earth and spring are the choices, to account for them in terms of changes in gravitational and elastic potential energy without letting anything outside the system to do work.
Figure 1 show the graph of the initial and final energies which will help to organize the energies needed to be taken into account.
Conclusion:
Therefore, the items included are box and the tracks surface because the kinetic friction increases the thermal energies and included this thermal energy internal to the system.
(b)

The value of
Answer to Problem 50PQ
The value of
Explanation of Solution
The reference configuration for the spring is when it is relaxed, and for gravity it is when the box is at the bottom of the ramp. The box is initially at rest
The energy conservation equation for a system is,
Here,
In this problem, Equation (I) will changes to (since all other energies are zero),
Write the expression for the initial gravitational potential energy.
Here,
Write the expression for the initial potential energy of the spring.
Here,
Write the expression for the thermal energy.
Here,
The total path length will be
Kinetic friction is proportional to the normal force which equals the weight.
Here,
Write the expression for the normal force.
Use equation (VIII) in equation (VI),
Use equation (VIII) in (VI), and solve for
Conclusion:
The displacement
Substitute
Therefore, the value of
Want to see more full solutions like this?
Chapter 9 Solutions
EBK PHYSICS FOR SCIENTISTS AND ENGINEER
- You pour a litre (1 kg) of 25.0˚C water into a 0.500 kg aluminium pan off the stove, but has previously been heated so it starts with a temperature of 120˚C. What is the temperature when the water and the pan reach thermal equilibrium (i.e., what is the temperature of both objects when they reach the same temperature)? Assume that the pan is placed on an insulated pad and a negligible amount of water boils off.arrow_forwardA golf club hits a golf ball and the golf ball’s flight reaches a maximum height of 5.48 m. Calculate the momentum of the golf ball at the maximum height if the mass of the golf ball is 0.459 kg.arrow_forward• Superposition Theorem • Thevenin's and Norton's Theorem 1. Find the unknown voltage V₁, unknown resistances R1 and R2, and currents flowing through R1 and R2 for the circuit shown below using Superposition Theorem. 40 V + R₁₂ w B C ♥16A 10A www 4A F ww 2 E Ꭰ 2. Use Thevenin's Theorem to find the current flowing in 3-ohm resistor and its power dissipation from the circuit shown in the right. + 3. Use Norton's Theorem for the same instruction as for No. 2. 8 V A www 202 B wwww 20 Ω 10 V + 302 202 www C - 12 V 502 www.arrow_forward
- Fill in blanksarrow_forwardA rock is dropped from a height of 2.00 m. Determine the velocity of the rock just before it hits the ground. If the momentum of the rock just before hitting the ground is 14.0 kg m/s, what is the mass of the rock? Is the collision between the rock and the ground elastic or inelastic? Explain.arrow_forwardDescribe how the momentum of a single ball changes as it free falls from a height of approximately 1 m, collides with a hard floor, and rebounds.arrow_forward
- • Nature of Resistance Temperature-Resistance Relationship Ohm's Law, Energy and Power Kirchhoff's Law • • Maxwell's Mesh Analysis 1. The steel of the third rail of a railway system has a resistivity of 21.4 μ-cm. If its cross-sectional area is 8.2 in², calculate the resistance per mile of rail, neglecting the effect of joints between sections. (1 point) 2. An incandescent lamp has a tungsten filament whose resistance is 96 at its operating temperature of 2900°C. Calculate the filament resistance when the lamp is disconnected from the electric source, under which condition its temperature is 24°C. (Use do = 0.0045 02/°C for tungsten) (1 point) 3. For the circuit shown, find the following: 50 V 602 10 V 702 a. the value of resistor R. (1 point) b. the equivalent resistance with respect to the 50-V source. (1 point) 4. For the circuit shown, determine all the currents in each branch using Kirchhoff's Laws. (3 points) A 5V 2 В -ний C 4 6 VT ww F E 5. Use Maxwell's Mesh to find I, and VAB…arrow_forwardFor items 8-9, refer to the problem below. Find all the currents flowing in every resistor, power dissipation in every resistor and the total power of the circuit shown at the right using... 8. Kirchhoff's Laws (5 pts) 9. Maxwell's Mesh Analysis (5 pts) A 8 V 10 V B + 20 Ω 3Ω 202 wwww C wwww 202 + 50 www 12 Varrow_forward• Nature of Resistance Temperature-Resistance Relationship Ohm's Law, Energy and Power Kirchhoff's Law • Maxwell's Mesh Analysis 1. A coil of copper wire (p = 10.37 2-cmil/ft) has a length of 600 ft. What is the length of an aluminum conductor (p 17 cmil/ft), if its cross-sectional area and resistance are the same as those of the copper coil? (Hint: Look for conversion of inches to mils and square inches to square foot. Include it in your solution.) (1 pt) 2. The copper field winding of an electric machine has a resistance of 46 at temperature of 22°C. What will be its resistance at 75°C? (Use do = 0.00427 /°C for copper) (1 pt) 3. The resistivity of a copper rod 50 ft long and 0.25 inch in diameter is 1.76 μ at 20°C. What is its resistance at - 20°C? (1 pt) 4. When two resistors A and B are connected in series, the total resistance is 36 2. When connected in parallel, the total resistance is 8 Q. What is the ratio of the resistance RA to resistance RB? Assume RA < RB. (1 pt) 5. The…arrow_forward
- 2. Two equally strong individuals, wearing exactly the same shoes decide to do a tug of war. The only difference is individual A is 2.5 meters tall and individual B is 1.5 meter tall. Who is more likely to win the tug of war?arrow_forward6. A car drives at steady speed around a perfectly circular track. (a) The car's acceleration is zero. (b) The net force on the car is zero. (c) Both the acceleration and net force on the car point outward. (d) Both the acceleration and net force on the car point inward. (e) If there is no friction, the acceleration is outward.arrow_forward9. A spring has a force constant of 100 N/m and an unstretched length of 0.07 m. One end is attached to a post that is free to rotate in the center of a smooth. table, as shown in the top view in the figure below. The other end is attached to a 1kg disc moving in uniform circular motion on the table, which stretches the spring by 0.03 m. Friction is negligible. What is the centripetal force on the disc? Top View (a) 0.3 N (b) 3.0 N (c) 10 N (d) 300 N (e) 1000 Narrow_forward
- Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage LearningPhysics for Scientists and Engineers with Modern ...PhysicsISBN:9781337553292Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningPrinciples of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning
- Physics for Scientists and EngineersPhysicsISBN:9781337553278Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningPhysics for Scientists and Engineers, Technology ...PhysicsISBN:9781305116399Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningCollege PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage Learning





