Question

A
A car running at 72 km/h
stops after covering
e distence of
lkm calculate the retardation?​

Answer 1

Answer:α=−25.5 rad/s  

2

Step-by-step explanation:Initial speed, v=72 km/h

⟹v=  

3600

72×10  

3

 

​  

 

⟹v=20 m/s

Distance, 2r=50 cm

⟹r=25×10  

−2

 m

Angular displacement, θ=20×2π

⟹θ=40π rad

Initial angular velocity, ω=  

r

v

​  

 

⟹ω=  

25×10  

−2

 

20

​  

 

⟹ω=  

5

4

​  

×10  

2

 

⟹ω=80 rad/s

Final angular velocity, ω  

′

=0 rad/s

From kinematics:

ω  

′2

−ω  

2

=2αθ (where α is angular acceleration)

⟹0−6400=2α×40π

⟹α=  

80π

−6400

​  

 

⟹α=−25.5 rad/s  

2