Concept explainers
According to the definition of mechanical work, pushing on a rock accomplishes no work unless there is _
a. movement.
b. a net force.
c. an opposing force.
d. movement in the same direction as the direction of the force.

The correct option to complete the statement, “According to the definition of mechanical work, pushing on a rock accomplishes no work unless there is”, from the following options,
movement.
a net force.
an opposing force.
movement in the same direction as the direction of the force.
Answer to Problem 1AC
Solution:
Option (d) is correct.
Explanation of Solution
Introduction:
According to the concept of mechanical work, net work is done on an object if it experiences a net force that brings a displacement in the object.
Explanation:
Reason for the correct options:
When direction of applied force and direction of movement are same then only maximum work will be done.
Hence, option (d) is correct.
Reason for the incorrect options:
Option (a) is incorrect because the movement can be perpendicular to the direction of the force. Now if the angle between the force and the displacement is 90 degrees, then the work done comes out to be zero. Hence, it is a wrong option.
Option (b) is incorrect because the presence of net force does not give any information about the displacement of object which is necessary for any work to be done.
Option (c) is incorrect because even if an opposing force is present, there is no movement or there is a movement but at a right angle. So, opposing force doesn’t imply that work is always done. Hence, it is a wrong option.
Hence, options (a), (b) and (c) are incorrect.
Conclusion:
A force will do work on an object only if it has a component in the direction parallel to the motion of the object. Thus, a push on a rock will accomplish work only when the movement of the rock is in the same direction as the direction of the force.
Want to see more full solutions like this?
Chapter 3 Solutions
Physical Science (12th Edition), Standalone Book
- Using the simplified energy balance in Equation 1, suppose there is heat transfer of 40.00 J to a system, while the system does 10.00 J of work. Later, there is heat transfer of 25.00 J out of the system while 4.00 J of work is done on the system. What is the net change in internal energy of the system?arrow_forwardYou 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_forwardFill 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_forward
- Describe 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_forward2. 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_forward
- University Physics Volume 1PhysicsISBN:9781938168277Author:William Moebs, Samuel J. Ling, Jeff SannyPublisher:OpenStax - Rice UniversityPrinciples of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningCollege PhysicsPhysicsISBN:9781305952300Author:Raymond A. Serway, Chris VuillePublisher:Cengage Learning
- Glencoe Physics: Principles and Problems, Student...PhysicsISBN:9780078807213Author:Paul W. ZitzewitzPublisher:Glencoe/McGraw-HillAn Introduction to Physical SciencePhysicsISBN:9781305079137Author:James Shipman, Jerry D. Wilson, Charles A. Higgins, Omar TorresPublisher:Cengage LearningPhysics for Scientists and Engineers with Modern ...PhysicsISBN:9781337553292Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning





