Question

Please Help Me

What is the acceleration of an object if it goes from a velocity of +25 m/s to rest in 5.0 seconds?


A.


–25 m/s2


B.


–5 m/s2


C.


+5 m/s2


D.


+25 m/s2



(1 pt)
Taking the direction west to be positive, and east to be negative, what is the average acceleration of a jet ski that goes from rest to 10 m/s west in 4 seconds?


A.


2.5 m/s2


B.


0.4 m/s2


C.


–0.4 m/s2


D.


–2.5 m/s2

Which moving body has no acceleration?


A.
a satellite orbiting at a constant speed


B.
a person running once around a track at a constant speed


C.
a car making a turn at a constant speed


D.
a person running 100 m straight across a field at a constant speed

Answer 1

1. a=Δv/Δt=(v-vo)/t=(0-25)/5=-25/5=-5 m/s²

The "-" sign shows us that the car has a slow motion

2.a=Δv/Δt=(v-vo)/t=(10-0)/4=10/4=2,5 m/s²

3.they do not have acceleration because they go at constant speed