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

Answer:

b) d = 0.71 Km

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

$v_o = 69\frac{mile}{hour} *1609.34\frac{meter}{mile} *\frac{1}{3600}\frac{hour}{s}=30.8 \frac{m}{s}$

$v_f= \frac{69}{2} \frac{mile}{hour} =34.5\frac{mile}{hour}=15.4 \frac{m}{s}$

a = -0.5 m/s²

Distance calculation

We replace data in the Formula (1)

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

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

$d =\frac{ 30.8^2 - 15.4^2}{2(0.5) }= 717.6m$

$d = 717.6 m\frac{1km}{1000m} = 0.7176Km$