A body moves with velocity 72km/h and after 5sec it takes brake then find the retardation?
Answers
Answered by
12
Answer
- Retardation = 4 m/s²
Given
- A body moves with velocity 72 km/h and after 5 sec it takes brake and goes to rest
To Find
- The retardation
Concept Used
- 1 st equation of motion
- v = u + at
- Acceleration and retardation are both same but opposite in direction
Solution
Initial velocity , u = 72 km/h = 72 × ⁵/₁₈ m/s
⇒ u = 20 m/s
Time , t = 5 s
Final velocity , v = 0 m/s
[ ∵ Goes to rest after applying brakes]
Acceleration , a = ? m/s²
Apply 1st equation of motion .
⇒ v = u + at
⇒ 0 = 20 + a(5)
⇒ 5a = - 20
⇒ a = - 4 m/s²
[ - ve sign of acceleration denotes retardation or deceleration ]
More Info
Answered by
13
• Given -
- Body moves with velocity of 72km/h & after 5 sec takes brake.
• To Find -
- The Retardation (Acceleration)
• Solution -
Here,
We have to do some conversions of given intervals,
★ Initial Velocity (u) - 20m/s
★ Time - 5sec
★ Final Velocity (v) - 0m/s .. (Brakes are applied. No motion)
Placing these values in 1st eqn of motion,
★ v = u + at
Placing values according to given Conditions,
➱ 0 = 20 + a (5)
➱ 5a = 0 - 20
➱ 5a = - 20
➱ a = -20/5
➱ a = -4 m/s²
⛬ Retardation of body is -4 m/s²
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