Question

A 10,000 kg engine exerts a force of 50 kN, to pull 4 wagons along the track as shown. If the track offers an opposing frictional force of 5 kN, calculate the acceleration of the train.

• A. $2.5m/s^2$
• B. $2.25m/s^2$
• C. $3.5m/s^2$
• D. $3.25m/s^2$

Answer 1

The correct option is B $2.25m/s^2$

Total mass of train,
$M=M_{engine}+4M_{wagon}$
$M=10,000+4\times 2500$
$M=20,000kg$

Net force acting on the train is:
$F_{net}=F_{train}-F_{friction}$
$F_{net}=(50-5)kN$
$F_{net}=45kN$

Applying Newton’s second law,
$F_{net}=Ma$
$45kN=20000a$
$a=\frac{45000}{20000}$
$a=2.25m/s^2$

Therefore, the acceleration of the train is $2.25m/s^2$.