A locomotive pulls a series of wagons. Which is the correct analysis of the situation?

A. because action always equals the reaction,the locomotive cannot pull the wagons,-the wagons pull backward just as hard as the locomotive pulls forward, so there is no motion.

B. The train moves forward because the locomotive pulls forward slightly harder on the wagons than the wagons pull backward on the locomotive

C. the locomotive gets the wagons to move by giving them a tug during which the force on the wagons is momentarily greater than the force exerted by the wagons on the locomotive

D. the locomotive can pull the wagons forward only if it weighs more than the wagons

E. The locomotive's force on the wagons is as strong as the force of the wagons on the locomotive,but the frictional force on the locomotive is forward and large while the backward fricitonal force on the wagons is small.

  1. 👍
  2. 👎
  3. 👁
  1. Very poor question.
    a. would be true if the word "accelerating" were inserted between "no motion". As it is, it is false
    b. if Locomotive pulls means net force of the locomotive, it is false, unless the train is accelerating.
    c. Again, true during the moment of acceleration.
    d. nonsense
    e. nonsense.

    So the question is what does the question mean "a locomotive pulls a series of wagons" This is very indefinite. The central question is the train accelerating, constant motion (including stopped)?

    I suspect Your instructor mean c to be the only right answer, but instructors get paid to do better than this.

    If net force is greater than ing force, acceleration happens. If net force is equal to ing force, acceleration is zero, and the system remains in whatever motion it was in.

    1. 👍
    2. 👎
  2. E is the correct answer. This question was written by a leading physics education researcher (I'm reading his book right now, in which he explains why the answer is E.)

    I can see how it would be easier if he said "accelerating," but questions like this are intended to be thought provoking, which is often better achieved by using less technical language.

    Bobpursley's explanation of "a" is incorrect. If he had written "accelerating" in there, E is still the only one that is correct. Bob's explanation would tell us that no train can ever accelerate, period. "A" could only be correct if he had specifically said the train is NOT accelerating.

    I will assume Bob means "net force ON the locomotive" since "net force OF..." doesn't make sense. Objects exert individual forces, they feel net forces. If it said "net force on the locomotive" in B, that answer would be essentially the same as E -- which is the correct answer, not a false one!

    D is clearly false. Weight is gravity pulling down, not train parts pulling forward or back. It's not relevant to the question. In other places, Bob seems to think that the question should have answer choices that are clearly true or clearly false. Here, he takes one that is clearly false and derides it as "nonsense."

    The third law requires that the force of the locomotive on the wagons be equal and opposite to the force of the wagons on the locomotive. If forward acceleration ever occurs, then there must be a net forward force on both locomotive, and wagons. With the wagon's, that's easy to explain. The locomotive pulls them forward. With the locomotive, if the wagons are pulling back, what is pushing it forward? It's the interaction with the tracks -- which must be stronger than the backward pull of the wagons.

    1. 👍
    2. 👎

Respond to this Question

First Name

Your Response

Similar Questions

  1. physics

    A locomotive is pulling an empty freight car with a constant acceleration on a horizontal surface. The mass of the locomotive is five times the mass of the car. Which statement is true about the force applied by the car on the

  2. math

    The speed of a locomotive without any wagons attached to it is 40 kmph. It diminishes by a quantity which is proportional to the cube root of the number of wagons attached. if the speed of the locomotive is 34 kmph when 27 wagons

  3. Science

    At a distance L equals to 400m from the traffic light, brakes are applied to a locomotive moving at a velociy VEquals to 54 km/hr. Determine the position of the locomotive relative to the traffic light l minute after application


    a locomotive pulls 10 identical freight cars. the force between the locomotive and the first car is 100,000 Newtons, and the acceleration of the train is 2m/s^2. there is no friction to consider.what is the force between the ninth

  1. Calculus - Alternating Series Test

    Determine whether the infinite series, sigma(((-1)^(n+1))/n)^2 converges or diverges. My professor gave these in a problem set after he taught the alternating series test. Simplying the series we get, sigma(((-1)^(n+1))/n)^2

  2. physics

    A locomotive is pulling 17 freight cars, each of which is loaded with the same amount of weight. The mass of each freight car (with its load) is 37,000 kg. If the train is accelerating at 0.7 m/s2 on a level track, what is the

  3. physics

    The position of a toy locomotive moving on a straight track along the x-axis is given by the equation x = t4 − 6 t2 + 9 t , where x is in meters and t is in seconds. The net force on the locomotive is equal to zero when t is

  4. math

    how is this series 3+ 9/4 +27/16 +81/64... is converge to 12? i represent the series as 3^(n+1)/4^n n starts from 0 to infinity, is this correct formula

  1. history

    Which wagons were used in the East but were not well suited for travel on the western trails? prairie schooners Mennonite wagons Conestoga wagons Ticonderoga wagons

  2. Physics

    Two toy locomotives approach each other along the same line, and upon collision both stop dead still. One locomotive has three times the speed of the other and the sum of their masses is 4.48 kg. What is the mass of the faster

  3. Theory of machines

    A locomotive is running at a constant speed of 100 km/ h. The diameter of driving wheels is 1.8 m. The stroke of the piston of the steam engine cylinder of the locomotive is 600 mm. Find the centripetal acceleration of the crank

  4. physics

    A locomotive is running at a constant speed of 100 km/ h. The diameter of driving wheels is 1.8 m. The stroke of the piston of the steam engine cylinder of the locomotive is 600 mm. Find the centripetal acceleration of the crank

You can view more similar questions or ask a new question.