The parent represents an inertial frame of reference. The parent would see the ball travel in a straight line, but by the time it got to the other side, the child who was meant to receive the ball would have moved away
Have you ever been travelling on a plane, train, or car and felt as though you weren’t moving? According to your frame of reference (the interior of the vehicle), you weren’t moving. However, according to someone standing on the ground, with the ground as their frame of reference, you were travelling at the speed of your vehicle. Both points of view are correct according to the frame of reference. Within this course, you will generally be dealing with inertial frames of reference. These frames of reference are either at rest or moving at constant speed when compared to the object being observed. The laws of physics are constant within inertial frames of reference. Non-inertial frames of reference are accelerating with respect to the object being observed. In these situations, forces seem to exist (fictitious force) to explain the motion of the objects. Fictitious forces do not really exist, since there is no real push or pull acting on the objects to cause their apparent motion.Example
Consider the following scenario: A train is in a station. There is a ball on the floor of a train car and there are two security cameras that are filming the ball’s motion as the train starts to accelerate away from the platform. The first camera is on the platform and is looking into the train car. The second camera is on the train car.Inertial frame of reference:The camera on the platform (stationary frame of reference) would see the ball roll but stay in place as the train accelerated underneath it. In this case, Newton’s 1st law is upheld since the ball which was initially at rest, stays at rest.Non-inertial frame of reference:The camera on the train (accelerating frame of reference) would see the ball spontaneously start to roll backwards. This violates Newton’s 1st law since the object at rest did not stay at rest. To make it seem as though Newton’s 1st law wasn’t violated, a fictitious force can be invented to “act” on the ball causing it to roll even though no push or pull on the ball actually occurred.Watch the video below to hear another explanation of reference frames:https://www.youtube.com/watch?v=wIzvfki5ozU&t=1s Question
The early models of the solar system were geocentric (Earth-centered). Would this be an inertial or non-inertial frame of reference? What would be the difficulties in describing the motion of the other objects in our solar system from this point of view?
Answer
· The geocentric model of the solar system is based on a non-inertial frame of reference. Even though the Earth’s speed is not changing, its direction is constantly changing with respect to the other objects in the solar system so it is an accelerating system. Our current heliocentric model, which was developed by Nicholas Copernicus, is based on an inertial frame of reference.· The difficulties of describing the motion of the other objects in our solar system from this point of view are that we would have to create fictional forces to account for retrograde motion of the planets.
Question
A child on an open style merry-go-round throws a ball to her friend on the opposite side of the circle. Describe the motion from the point of view of the child and from the point of view of a parent watching from the side. Identify the type of frame of reference in each point of view.
Answer
· Since the child is constantly changing direction and thus accelerating, she is in a non-inertial frame of reference. From her perspective, the ball would follow a curved path and would not reach her friend because a fictitious centrifugal force caused it to curve away.