Answer:
You need at least 2.8 s to slow down your car to 100 km/h. If we add reaction time (≅0.3 s), you will need 3.1 s.
Explanation:
Hi there!
The equation of velocity for an object moving in a straight line is the following:
v = v0 + a · t
Where:
v = velocity at time t.
v0 = initial velocity.
a = acceleration.
t = time.
We have to find the time at which the velocity is 100 km/h with a decceleration of 4.9 m/s² and an initial velocity of 149 km/h. Let´s first convert km/h into m/s:
149 km/h · (1000 m / 1 km) · ( 1 h / 3600 s) = 41.4 m/s
100 km/h · (1000 m / 1 km) · ( 1 h / 3600 s) = 27.8 m/s
Now, let´s solve the equation of velocity for the time:
v = v0 + a · t
(v - v0) / a = t
Replacing with the data:
(27.8 m/s - 41.4 m/s) / -4.9 m/s² = t
Notice that the acceleration is negative because you are slowing down.
t = 2.8 s
You need at least 2.8 s to slow down your car to 100 km/h. If we add reaction time (≅0.3 s), you will need 3.1 s.
