A vehicle was moving at a speed of 90 km/h. On seeing a baby 20 m ahead on the road, the driver jammed on the brakes and it came to rest at a distance of 15 m. What is its retardation and how long does it take to come at rest?
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Answered by
0
v = 0
u = 90 km/hr = 20m/s
s = 15 m
a = ?
by using third equation of motion
v² = u² + 2as
0² = 20² + 2(a)15
0 = 400 + 30a
-400= 30a
a = -400/30
a = - 13.33 m/s² (approx)
Answered by
4
Answer:
acceleration= -20.8 m/s^2
Explanation:
Given
→U = 90 km/hr = 90 x 5/18 m/s = 25 m/s
→distance travelled till velocity becomes zero = 15m
→V= 0 m/s (stopped)
V^2 - U^2 = 2as
(0)^2 - (25)^2 = 2(a)15
- 625 = 30(a)
a= -625/30= -20.8m/s^2. (minus shows retardation/acceleration is decreasing)
v=u+at
0 = 25 - 20.8 (t)
20.8(t)= 25
t = 25/20.8
t=1.2 seconds
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