Answer:
It takes 1.67 seconds to reduce its speed to the legal limit
Explanation:
The main point in this problem is the difference between the units of
the speeds and acceleration
The unit of the speeds is km/hour
The unit of the acceleration is m/sec²
So we must to change the units of the speeds from km/hour to
meter/second
1 km = 1000 m
1 hour = 60 × 60 = 3600 seconds
Then 120 km/hr = m/s
96 km/hr = m/s
To find the time of deceleration (to reduced the speed) we will use:
v = u + at. where u is the initial velocity, v is the final velocity, a is the
acceleration and t is the time
v = 26.67 m/s , u = 33.33 m/s , a = - 4 m/s²
Substitute these values in the rule
26.67 = 33.33 + (- 4)t
Subtract 33.33 from both sides
- 6.66 = - 4t
Divide both sides by - 4
t = 1.67 seconds
<em>It takes 1.67 seconds to reduce its speed to the legal limit</em>