Question on Newton's law of motion

In summary, the conversation discusses a train consisting of three coaches, two of which have engines and one is un-powered. The forces exerted on each coach and their respective masses are given, and the question asks for the net force on coach A. The correct answer is achieved by considering the forces on the entire train and using Newton's second law, resulting in a net force of 0.61m/s2.
  • #1
gaobo9109
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0

Homework Statement


A train consists of three coaches A,B and C linked together via tow bars. A and C are coaches with engines and have a mass of 10000kg each, while B is an un-powered coach having a mass of 8000kg. The driving force of the engines in A and C are 20000N and 18000N respectively. The drag force on A is 9000N while B and C experiences the same drag force of 6000N.


Homework Equations


Newton's three laws


The Attempt at a Solution


I tried to find the net force exerted on coach A by
F(net) = 20000 - 9000 = 11000N
a = 11000/10000 = 1.1m/s2
However, the answer given is 0.61m/s2
Can anyone tell me where did I go wrong? Thanks
 
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  • #2
Hi Gaobo,

The question gives you extra information which you haven't used which is key to getting answer.
I suggest you draw a picture and consider the entire train, currently you have missed the forces relating to coaches B and C.

Hope this helps
 

1. What are Newton's laws of motion?

Newton's laws of motion are three fundamental laws that describe the behavior of objects in motion. They were developed by Sir Isaac Newton in the 17th century and are still used today to explain the motion of objects.

2. What is the first law of motion?

The first law of motion, also known as the law of inertia, states that an object at rest will remain at rest, and an object in motion will remain in motion at a constant velocity, unless acted upon by an external force.

3. What is the second law of motion?

The second law of motion, also known as the law of acceleration, states that the acceleration of an object is directly proportional to the net force acting on the object and inversely proportional to its mass. This can be expressed as the equation F=ma, where F is the net force, m is the mass of the object, and a is the acceleration.

4. What is the third law of motion?

The third law of motion, also known as the law of action and reaction, states that for every action, there is an equal and opposite reaction. This means that when one object exerts a force on another object, the second object will exert an equal and opposite force on the first object.

5. How are Newton's laws of motion used in everyday life?

Newton's laws of motion are used in many aspects of everyday life, from the movement of vehicles and airplanes to the motion of sports equipment. They are also used in engineering and design to create efficient and effective machines and structures. Additionally, understanding these laws can help us predict and explain the behavior of objects in our surroundings.

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