A (n) 26000 kg freight car is rolling along a track at 3.3 m/s. Calculate the time needed for a force of 1150 N to stop the car. Answer in units of s.

The time = 74.61 s.

Explanation:

From Newton's Third law of motion,

The force needed to stop is equal and opposite to the propelling force from the engine of the freight car.

F = ma ... Equation 1

Where F = force needed to stop the the freight car, m = mass of the freight car, a = acceleration of the freight car.

a = F/m ... Equation 2.

Given: F = - 1150 N (Opposite in direction to the motion of the car) m = 26000 kg.

Substituting into equation 2

a = - 1150/26000

a = - 0.04423 m/s²

Also

v = u + at

t = (v-u) / a ... Equation 3

Where t = time needed for the force to stop the car, v = final velocity, u = initial velocity, a = acceleration.

Given: u = 3.3 m/s v = 0 m/s (brought to rest), a = - 0.04423 m/s²

Substituting into equation 3

t = (0-3.3) / -0.04423

t = - 3.3/0.04423

t = 74.61 sec.

Thus the time = 74.61 s