Intro to Acceleration Video Lessons

Concept

# Problem: (a) A light-rail commuter train accelerates at a rate of 1.35 m/s2. How long does it take to reach its top speed of 80.0 km/h, starting from rest? (b) The same train ordinarily decelerates at a rate of 1.65 m/s2. How long does it take to come to a stop from its top speed? (c) In emergencies the train can decelerate more rapidly, coming to rest from 80.0 km/h in 8.30 s. What is its emergency deceleration in m/s2?

###### FREE Expert Solution

Final velocity:

$\overline{){{\mathbf{v}}}_{{\mathbf{f}}}{\mathbf{=}}{{\mathbf{v}}}_{{\mathbf{0}}}{\mathbf{+}}{\mathbf{a}}{\mathbf{t}}}$

(a)

• t = ?
• a = 1.35m/s2
• v0 = 0m/s
• vf = 80.0 km/h(1000m/1km)(1h/60min)(1min/60s) = 22.22 m/s
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###### Problem Details

(a) A light-rail commuter train accelerates at a rate of 1.35 m/s2. How long does it take to reach its top speed of 80.0 km/h, starting from rest?

(b) The same train ordinarily decelerates at a rate of 1.65 m/s2. How long does it take to come to a stop from its top speed?

(c) In emergencies the train can decelerate more rapidly, coming to rest from 80.0 km/h in 8.30 s. What is its emergency deceleration in m/s2?