Calculate Train Speed Increase: 84 km/h in 495.7s | Force Physics Problem

Click For Summary

Homework Help Overview

The problem involves calculating the time required for a freight train to accelerate from rest to a speed of 84 km/h, given its mass and the force exerted by the locomotive. The subject area pertains to dynamics and kinematics in physics.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the conversion of speed from km/h to m/s and the application of Newton's second law (F=ma) to find acceleration. There are questions about the correctness of the calculated time and its representation in different units.

Discussion Status

Some participants express uncertainty about the correctness of the time calculation, with one participant noting a significant difference from an expected answer. Others clarify that the time should be expressed in minutes, leading to a conversion that aligns with the problem's requirements.

Contextual Notes

There is a focus on ensuring the answer is presented in the correct units as specified by the problem, which has led to some confusion among participants regarding the conversion process.

mandy9008
Messages
127
Reaction score
1

Homework Statement


A freight train has a mass of 1.4x107 kg. If the locomotive can exert a constant pull of 6.7x105 N, how long does it take to increase the speed of the train from rest to 84 km/h?

Homework Equations


F=ma
a=v/t

The Attempt at a Solution


I converted 84 km/h into 23.3 m/s.
F=ma
6.7x10^5 N=1.4x10^7 m (a)
a= .047 m/s^2

a=v/t
.047 m/s^2=(23.3 m/s)/t
t=495.7s --> 2.97x10^4 min
 
Last edited:
Physics news on Phys.org


That looks correct.
 


when I enter it it says that it differs significantly from the correct answer
 


mandy9008 said:
when I enter it it says that it differs significantly from the correct answer

the t =2.97x104 min is not correct.

t= 495.7 s should be correct.
 


the question asks for time in minutes
 


i converted it and got 8.26 min and got it correct.i don't know what i was thinking converting it before haha thanks
 

Similar threads

  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 22 ·
Replies
22
Views
4K
  • · Replies 2 ·
Replies
2
Views
7K
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
1
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
4
Views
3K
Replies
5
Views
7K
  • · Replies 4 ·
Replies
4
Views
2K