Posterous theme by Cory Watilo

Corrections to Questions on Acceleration

1.  A car changes its velocity by 30 m/s in 5 seconds, what is the acceleration of the car?

v=30m/s

t=5s

a=∆v/∆t

a=30/5

a=6m/s2

2.  A bike starts from rest and accelerates to 20 m/s  over a period of 6 seconds. What is the acceleration of the car?

v=20m/s

t=6s

a=∆v/∆t

a=20/6

a=3.33m/s2

 

3.  A man moving at 2 m/s accelerates at a rate of 3 m/s2 for 2.5 seconds. What is the new velocity of the man?

a=3m/s2

t=2.5s

ax∆t=∆v

3x2.5=∆v

v=7.5m/s

                             a=v-u/∆t   

               3=v-2/2.5

               V=9.5m/s

 

4.  A car decelerates from 60 m/s to 20 m/s at a rate of -5 m/s2. How long does this deceleration take the car?

v= -40m/s

a= -5m/s2

t=∆v x a

t=-40x-5

t=200s

a=v-u/∆t

               -5=20-60/t

               t=8s