CHAPTER 21. MOTION IN ONE DIMENSION 21.7
Step 5:Substitute the values and calculate the final velocity
~vf = ~vi+at
~vf = 0m·s−^1 + (8m·s−^2 )(4s)
= 32m·s−^1 East
Step 6:Time at half the distance: Find an equation to calculate the time
We can use Equation 21.3:
∆~x = ~vi+^12 ~at^2
32 m = (0m·s−^1 )t+^12 (8m·s−^2 )(t)^2
32 m = 0 + (4m·s−^2 )t^2
8 s^2 = t^2
t = 2, 83 s
Step 7:Distance at half the time: Find an equation to relate the distance and
time
Half the time is 2 s, thus we have~vi,~aandt- all in the correct units.
We can use Equation 21.3 to get the distance:
∆~x = ~vit+^12 at^2
= (0m·s−^1 )(2s) +^12 (8m·s−^2 )(2s)^2
= 16 mEast
Exercise 21 - 7
1. A car starts off at 10 m·s−^1 and accelerates at 1 m·s−^2 for 10 s. What is its
final velocity?
Physics: Mechanics 429