frames of reference and motion of ball (1 Viewer)

[Danger]

These are some frames of reference. Each contains a ball which is dropped from the ceiling of the frame. Classify each as an inertial or a non inertial frame of reference and describe the motion of the ball when allowed to drop:

a) earth car moving forward with constant velocity
b) earth lift. cable snapped and in free-fall.
c) earth car accelerating
d) earth car braking.

 

[watatank]

inertial frame of reference is where there is no acceleration. so that's constant velocity or at rest (think newton's first law).

a) inertial, ball would go straight down
b) non inertial, ball would go straight down, not sure how fast it would go relative to the lift
c) non inertial, ball will go backwards relative to the cars motion (if the car accelerates it means that it is going faster than the ball inside it when it drops)
d) non inertial, ball will go forward (if car is slowing down, the ball when dropped is going faster than the car)

 

[Danger]

so nothing is with constant velocity unless it is actually stated?

I dont quite get d)

wouldnt the ball only go forward when the car is reversing, not slowing down? I think the car may be slowing down, but it is still going in a forward motion. please correct me if im wrong

Thanks btw

 

[Mark576]

Think about when you're in a car, and then the driver suddenly brakes. You are pushed against the seatbelt. This is due to inertia, as stated by Newton in his first law of motion. You want to continue moving at the same velocity as you were before the car began to decelerate. The same principle applies in this non-inertial frame of reference.