Question

If you were to a derail an 8,000,000 kg train that is traveling 10 m/s, how long will it take to bring it to a stop if a 2 kN frictional force is applied?

Answer 1

40,000 s

Step-by-step explanation:

Find the acceleration of the train given the mass and the force applied.

Convert 2 kN to N --> 2000 N.

Substitute the train's mass and applied force into Newton's 2nd Law:

• F = ma
• 2000 = 8,000,000 * a
• a = 0.00025 m/s²

SInce the train is slowing down, the acceleration should be negative.

Using the acceleration, initial velocity, final velocity, we can solve for time using this kinematic equation:

• v = v₀ + at
• 0 = 10 + (-.00025)t
• -10 = -.00025t
• t = 40000 s

It will take 40,000 seconds to bring the train to a stop if a 2 kN frictional force is applied.