Question

A car moves with constant acceieration of -0.s m/s? on a straight portion of the road. Att- 0s the car has a velocity of 69 mph, how far does the car travels until its speed is reduced to haif? Select one: a. 1.12 km o b.0.71 km c. 3.57 km d. 1.02 km

Answer 1

b) d = 0.71 Km

Step-by-step explanation:

Car kinematics

Car 1 moves with uniformly accelerated movement

`v_f^2=v_o^2+2a*d` Formula (1)

d: displacement in meters (m)

v₀: initial speed in m/s

vf: final speed in m/s

a: acceleration in m/s²

Equivalences:

1mile = 1609.34 meters

1 hour = 3600s

1km = 1000m

Known data

`v_o = 69(mile)/(hour) *1609.34(meter)/(mile) *(1)/(3600)(hour)/(s)=30.8 (m)/(s)`

`v_f= (69)/(2) (mile)/(hour) =34.5(mile)/(hour)=15.4 (m)/(s)`

a = -0.5 m/s²

Distance calculation

We replace data in the Formula (1)

`15.4^2 = 30.8^2+2(-0.5)*d`

`2(0.5)*d = 30.8^2 - 15.4^2`

`d =( 30.8^2 - 15.4^2)/(2(0.5) )= 717.6m`

`d = 717.6 m(1km)/(1000m) = 0.7176Km`