I have a question about a problem regarding Newton's third law.
a. An iron rod is held up by a magnet. The magnet is held up by a string (from a ceiling, let's say). Draw a free-body diagram for the magnet and a separate free-body diagram for the iron rod.
For the rod I have a gravitational force going downward, and magnetic force pointing upward and a contact force pointing downward.
For the magnet I have a gravitational force pointing downward and a tension force and contact for pointing upward.
Is this correct?
b. For each of the forces drawn, identify the corresponding force that completes the Newton's third law pair.
I know the two contact forces are pairs, but am unclear about the other pairs.
No. THe rod has gravity down, magnetic force up equal to the rods'weight. For the magnet, gravity down equal to rods weight, magnetic force up. THen for the string, magnetic and rod weight down, and tension up equal to that weight.
I don't agree with Bob's answer here. The iron rod is not levitating here (it's theoretically possible, but I don't think that is meant here), so we must assume that it is in contact with the magnet.
"For the rod I have a gravitational force going downward, and magnetic force pointing upward and a contact force pointing downward."
This is correct.
"For the magnet I have a gravitational force pointing downward and a tension force and contact for pointing upward."
Here you forgot the magnetic force exerted by the rod on the magnet. This force is pointing downward.
Besides the tension forces you have the magnetic forces as third law pairs.
If you consider the other forces (the tension force and the gravitational force), you must include the objects in which that force is exerted.
So, the tension force exerted by the sring is on the magnet is opposite to the force exerted by the magnet on the string.
The gravitational force exerted by the Earth on the rod is opposite to the gravitational force exerted by the rod on the entire Earth. Sounds strange but it is true! And the same is true for gravitational force exerted on the magnet.
Answer this Question
A 1.13 kg ball is connected by means of two ideal strings to a vertical, rotating rod. The strings are tied to the rod and are taut. The upper string is 24.0 cm long and has a tension of 31.5 N, and it makes an angle θ2 = 51.0° with the rod, while the
- asked by Charlie
- 1,611 views
A 32.2 g iron rod, initially at 22.3 C, is submerged into an unknown mass of water at 63.9 C, in an insulated container. The final temperature of the mixture upon reaching thermal equilibrium is 58.6 C. What is the mass of the water?
- asked by HELP
- 7,711 views
Science check answer quick!
I really do not understand Number 7 Which of these does Newton's law of universal gravitation imply? (Points : 1) The force of gravity between two objects is inversely proportional to the product of the two masses.
- asked by Gianna
- 6,476 views
Why is Newton’s cradle (Newton’s balls) described as an “almost-ideal” closed system?
- asked by jasmine
- 3,423 views
What were the effects of the Zhou metal workers mastering iron? Select the two correct answers. A. The Zhou conquered the warlords and were the first to unify China. B. Iron made stronger, more effective farm tools and increased crop yield. C. Iron weapons
- asked by Abubudah
- 2,658 views
When you drop a 0.36 kg apple, Earth exerts a force on it that accelerates it at 9.8 m/s^2 toward the earth's surface. According to Newton's third law, the apple must exert an equal but opposite force on Earth. If the mass of the earth 5.98x10^24 kg, what
- asked by Jenna
- 6,433 views
According to the following reaction, how many grams of iron(III) chloride will be formed upon the complete reaction of 27.1 grams of chlorine gas with excess iron? The balanced eq is 2Fe+3Cl2=2FeCl3 Here is my worked out equation: 27.1g Cl*1 mol Cl/35.46 g
- asked by Kylee
- 2,024 views
Physics (Conservation of momentum)
1. Which of Newton’s laws of motion states that an object at rest stays at rest and an object in motion stays in motion with the same speed and the same direction unless acted upon by an unbalanced force? A. Newton's Third Law of Motion B. Newton's
- asked by BingoB
- 4,113 views
An apparatus is designed to study insects at an accelera�tion of magnitude 980 m/s 2 ( = 100 g). The apparatus consists of a 2.0-m rod with insect containers at either end. The rod rotates about an axis perpendicular to the rod and at its center. (a) How
- asked by hurrent
- 489 views
A box,is resting on a smooth(frictionless)table.The mass of the box is 10 kg. (a)Determine the weight of the box and the normal force acting on(b)If the box is pushed down with a force of 40 Newton determine the normal force(c) If the box was pulled up
- asked by Jodie
- 2,092 views
Write the dissociation equation for iron(II) ammonium sulfate hexahydrate in water . Fe(NH4)2(SO4)2 * 6H2O --> __?________ I know dissociate means to take apart so for example; NaCl would look like Na^+ + Cl^- And another one like: Fe2(SO4)3 would look
- asked by Christine
- 4,233 views
A slab of metal of volume V is made into a rod of length L. The rod carries current I when the electric field inside is E.Find the resistivity of the metal?
- asked by Spencer
- 1,079 views
1. Which of the following statements about Newton's Third Law is the most true? a The forces acting upon two objects are dependent on the initial velocities of the objects b The law of conservation of momentum is obeyed in all systems c The two objects
- asked by Bride
- 2,638 views
Which option accurately describes the significance of the scientific theories of Isaac Newton? A. Newton’s theories helped scientists understand the significance of germs and sterilization. B. Newton’s theories helped scientists understand the
- asked by michael
- 5,749 views
A metal rod is 40.125 cm long at 20 °C and 40.148 cm long at 35 °C. calculate the coefficient of linear expansion of the rod for this temperature range.
- asked by selena
- 2,743 views
According to Newton's Second Law of Motion, in which of these situation is the object accelerating. A) A book on a shelf B) A rock hitting the ground C) a helium balloon tied to a lamp post D) a ball that has been thrown upward
- asked by E
- 1,803 views
The ladle at an iron foundry can hold 8500 kg of molten iron. You need 646 metric tons of iron to make rails. How many ladlefuls of iron will it take to make 646 metric tons of iron? (note - 1 metric ton = 1000 kg
- asked by evens
- 400 views
Physics (Newton's and Coulomb's Laws) **ASAP**
1. Which law gives the force between two objects that is related to their mass and distance? A. Newton's law of gravitation B. Coulomb's law C. Kepler's law D. Newton's second law of motion 2. What is the property that allows a positive proton and a
- asked by Trey
- 1,672 views
Rod a is twice as long as rod b, rod c is 1/12m shorter than rod b. If rod c is 1/6m long, find the total length of Rod a and Rod b I thought it would be 2x+(x+1/12)+1/6
- asked by Reine
- 610 views
The free-body diagram in the drawing shows the forces that act on a thin rod. The three forces are drawn to scale and lie in the plane of the screen. Are these forces sufficient to keep the rod in equilibrium, or are additional forces necessary f3 ' ' ' f1
- asked by Panda
- 1,455 views