Question

A girl starts from rest and reaches a walking speed of 1.4 m/s in 3.0 s. She walks at this speed for 6.0 s. The girl then slows down and comes to a stop during a 10.0 s period. What was the girls acceleration at each of the three time periods?

Answer 1

1) The girl's acceleration at time 't' is,
`a=0.47` m/s²

2) The girl's acceleration at time 't₁' is,
`a_(1)=0` m/s²

3) The girl's acceleration at time 't₂' is,
`a_(2)=-0.14` m/s²

Step-by-step explanation:

Given data,

The initial walking speed of the girl, u = 0

The speed of the girl at the time 't' 3 s is, v₁ = 1.4 m/s

The time period the girl walked at the speed 1.4 m/s is, t₁ = 6 s

The girl slows down and comes to a stop during a period, t₂ = 10 s

1) The girl's acceleration at time 't'

`a=(v-u)/(t)`

`a=(1.4-0)/(3)`

`a=0.47` m/s²

2) The girl's acceleration at time 't₁'

`a_(1) =(v_(1) -v)/(t_(1))`

`a_(1)=(1.4-1.4)/(6)`

`a_(1)=0` m/s²

3) The girl's acceleration at time 't₂'

`a_(2) =(v_(2) -v_(1))/(t_(2))`

`a_(2)=(0-1.4)/(10)`

`a_(2)=-0.14` m/s²