A 500 tonne train collides with a station emergency buffer stop while travelling at 2 ms-1. The buffer stop has a mass of 1.5 to
1 answer:
Answer:
a) Δx=1.41 m; b) a=1.41 m/(s^2)
Explanation:
a) To solve this problem, we should consider two processes:
1) inelastic collision between the train and the buffer;
2) motion of the pair to reach complete stop.
As the collision between the train and the buffer is inelastic, we have some energy wasted. However, the velocity after the collision can be determined using Momentum Conservation Law:
mtVt=(mt+mb)*V, where mt- mass of the train, mb- mass of the buffer, Vt- initial velocity of the train, V- velocity after the collision.
V=mtVt/(mt+mb)=1.994 m/s.
After train and buffer have collided, the motion can be described using Energy Conservation Law, where kinetic energy of the buffer-train couple is fully transmitted to the potential energy of elastic deformation of the spring. From this idea, the following equation can be derived:
, where x- displacement of the spring, K- spring stiffness.
From this equation, we can find:
Regarding an approximation, we can assume, that the buffer is mass-less in comparison with the train and this assumption will yield very small error. If we consider mass-less buffer, there is no need to use mass of the buffer in calculations and there is no need to consider collision and finding velocity after the collision. To support this assumption, we can compare initial velocity of the train and final during the collision- train slowed down from 2m/s to 1.994 m/s- the change is insignificant, so we can directly apply Energy conservation law to the train-spring system and avoid buffer's mass.
b) To find mean acceleration, we can use the following known values: initial velocity is 1.994 m/s and the traveled length is 1.41 m. As we are looking for the mean value, we can assume, that the acceleration was constant and the following equation can be used: , where a- mean acceleration, V- velocity of the train and x- traveled distance.
From this equation, we can find acceleration as:
This acceleration is significantly smaller, than g (gravitational acceleration), so it is not dangerous to the passengers.
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Answer:
a) E = b) i.
Explanation:
Assuming no other forces acting on the electron, as the field is pushing the electron back till it comes to rest momentarily, applying the work-energy theorem, the loss in kinetic energy, must be equal to the work done by the field on the electron.
The force that does work on the electron is the one due to the electric field E, and by definition of electric field, can be expressed as follows:
W = q*E = -e*E (1)
This work must be equal to the change in Kinetic Energy:
ΔK = Kf -K₀ = 0 - K = -K (2)
From (1) and (2), and solving for E, we have:
E =
b) As the electric field (by convention) has the direction that it would have a positive test charge, the electrons (being negative charges),when starting from rest),have the direction opposite to the field.
In this case, as the electron has an initial velocity, and the field is opposing to the electron movement, we conclude that the electric field is in the direction of the electron´s motion, due to the electron slows down, and then comes momentarily to an stop, before changing direction and move opposite to the field as it is its natural behavior.
The code to
- Declare a variable and increment with a while loop until the variable is not less than 5
- Create a function that returns the product of two numbers
- Uses the new keyword to create an array
were written in JavaScript and are found in the attached images
<h3>Declaring a variable</h3>The first code declares a variable called num and gives it an initial value of 0. It then enters a while loop that lauches a message box (using <em>window.alert</em>) to print the message "<em>Keep going</em>" as long as num remains less than 5.
If nothing is done within the loop to increment num towards the value 5, the loop will go on endlessly notifying the user to "<em>Keep going</em>".
So, an increment of 1 was added to the loop body to increment the variable num. This makes sure the loop terminates.
<h3>Creating a function that returns the product of two numbers</h3>Here, a function was created that receives two arguments (n1 and n2), then returns the product (n1 * n2)
<h3>Declaring an Array</h3>This last code segment creates an array using the new keyword. The new keyword is generally used in constructing objects.
In this case the object constructed is an array having three strings;
- my <em>first name</em>
- my <em>nickname</em>, and
- my <em>last name</em>
See another solved JavaScript problem here brainly.com/question/23610566
