Answer :
The question involves calculating the Tractive Effort (TE) required to move a 12,000 ton freight train on a level track at 60 mph, given a rolling resistance coefficient (K) of 0.07. The answer includes an explanatory step-by-step calculation for the rolling resistance component of TE, highlighting that other resistive forces are not considered without further information.
The question is about calculating the Tractive Effort (TE) required for a freight train to move on level tangent track at a speed of 60 mph. To calculate TE, we need to use the formula TE = total resistance x weight of the train, where total resistance includes rolling resistance and any other forces opposing the train's motion (usually air resistance). Given that K (rolling resistance coefficient) is 0.07, and the train’s total weight is 12,000 tons (which equals 24,000,000 pounds as 1 ton = 2000 pounds), we can calculate the rolling resistance. However, without the specific values for air resistance and other potential resistive forces, we can only estimate the TE based on rolling resistance.
Calculation step:
- First, convert the weight of the train to pounds, if given in tons. Here, it is already provided in pounds.
- Next, calculate the rolling resistance: Rolling Resistance = K x weight of the train = 0.07 x 24,000,000 lb.
- Finally, calculate the TE which will be equal to the rolling resistance, as no other resistive forces were given or asked to be considered.
This method approximates the rolling resistance portion of the tractive effort necessary at the given speed on level track. However, for a complete answer, one would also need to take into account the dynamic resistance, which increases with speed, and could be significant at 60mph.
