a bus decrease its speed from 40 km/hr to 30 km/hr in 2 sec find acceleration
Answers
Given :
Initial velocity of the bus : 40 km/hr
Final velocity of the bus : 30 km/hr
Time taken : 2 sec
To find :
The acceleration of the bus.
Solution :
Firstly we have to convert km/hr to m/s
we know that,
» 1km/hr = 5/18km/hr
» 40km/hr = 40 × 5/18 = 11.1 m/s
» 30km/hr = 30 × 5/18 = 8.3 m/s
Accerlation is the rate of change of velocity.
- It is a vector quantity having both magnitude as well as direction.
- SI unit of acceleration is metre per second square.
As we are provided with initial velocity, final velocity and time we can use first equation of kinematics that is,
v = u + at
- v denotes final velocity
- u denotes initial velocity
- a denotes acceleration
- t denotes time taken
by substituting all the given values in the formula,
➝ v = u + at
➝ 8.3 = 11.1 + a(2)
➝ 2a = 8.3 - 11.1
➝ 2a = -2.8
➝ a = - 2.8/2
➝ a = - 1.4 m/s²
Thus, the acceleration of the bus is -1.4 m/s².
If the speed is decreasing with time then accerlation is negative. The negative accerlation is called deceleration or retardation.
Know more :
First equation of kinematics : v = u + at
Second equation of kinematics : s = ut + 1/2at²
Third equation of kinematics : v² - u² = 2as
Answer:
- -1.39 m/s² is the acceleration of the bus.
Explanation:
We have,
- Initial velocity (u) = 40 Km/h
- Final velocity (v) = 30 Km/h
- Time taken (t) = 2 sec
To find,
- Acceleration (a)
Solution,
>> Initial velocity (u):
=> 40 × 5/18
- 11.11 m/s
____________________
>> Final velocity (v):
=> 30 × 5/18
- 8.33 m/s
____________________
>> Time taken (t):
- 2 sec
______________________
>> Acceleration (a):
=> Change in velocity/Time taken
=> v - u/t
=> 8.33 - 11.11/2
=> -2.78/2
=> -1.39
______________________
∴ The acceleration of the bus is -1.39 m/s² or retardation of the bus is 1.39 m/s².