Section 2.17 - Interactive checkpoint: subway train



		A subway train accelerates along a straight track at a constant 1.90 m/s². How long does it take the train to increase its speed from 4.47 m/s to 13.4 m/s?

Diagram [Hide]

Variables [Hide]
Fill in the known values.
Variable	Value
acceleration	a = m/s²
initial velocity	v_i = m/s
final velocity	v_f = m/s
elapsed time	Δt
I think I'm done.	I need help. Show the correct values.

Strategy [Hide]

Select an equation that contains variables for the values you are given, and the one you want to calculate.
Remember that the delta symbol Δ stands for a change. It means the final value minus the initial value. To solve the problem, expand the term that contains the Δ.

Physics principles and equations [Hide]

v = Δx/Δt

a = Δv/Δt

Step-by-step solution [Hide]
2	Select the equation that contains variables for the values you are given, and the one you want to calculate.
Expand equation	The delta symbol Δ stands for a change. The change in velocity is equal to the final velocity minus the initial velocity. a = (v_f – v_i)/Δt
Solve for elapsed time	Δt = (v_f – v_i)/a
Enter values	Δt = ( m/s – m/s) / ( m/s²)
Evaluate	Δt = s