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

Answer:

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

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'

                                $a=\frac{v-u}{t}$

                                $a=\frac{1.4-0}{3}$

                               $a=0.47$ m/s²

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

                                $a_{1} =\frac{v_{1} -v}{t_{1}}$

                                $a_{1}=\frac{1.4-1.4}{6}$

                               $a_{1}=0$ m/s²

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

                                $a_{2} =\frac{v_{2} -v_{1}}{t_{2}}$

                                $a_{2}=\frac{0-1.4}{10}$

                               $a_{2}=-0.14$ m/s²