![]() ![]() I would then summarise the definitions and equations. I would then sum up how this relates to the key equations that arise from the graph including displacement. I would get them to do little experiments with a toy car to demonstrate these points. I would then go on to talk in the context of the car example how the line would change as the car picks up speed, slows down, and how this relates to acceleration. We get a straight horizontal line from the origin to 5 seconds on the x-axis. So if we plot a point at each second of the velocity of the car. We see that the time goes by, but neither the direction or speed of the car changes. Imagine watching a stationary car for 5 seconds. Time is drawn on the x-axis because it is the variable the scientist chooses to change (independent) and velocity is drawn on the y-axis because it is what the scientist measures (dependent). Then when we think about acceleration, we want to know how much the velocity is changing over time.Ī velocity time graph is what we use to show how velocity changes with time. When we talk about speed every day we mean the distance something moves in a particular time, but generally physicists prefer to talk about velocity - distance moved in a particular time in a particular direction - known as displacement. When solving these problems, do the following: (1) Identify your known quantities, (2) Determine what's being asked, and (3) Select the best equation to solve the problem.The first step in answering any question is to figure out what the question really means! Velocity is a term physicists use to describe not just speed, but speed in a particular direction. ![]() How this affects the quantities of velocity, distance and time are represented by the following m otion equations:Ī = vf/t (for an object starting from rest vf is final velocity ).Ī = acceleration, t = time, d = displacement (change in position) A free falling object has an acceleration of -9.8m/s2. Said object will experience a pure acceleration due to gravity (and nothing else). Standard unit is (g).Īn object in free fall is an object acted upon by gravity alone. This is when gravity pulls down on falling objects. Values are typically written as m/s/s m/s2, mi/hr/s, or km/hr/s. Since acceleration is a velocity change over time, the unit is a velocity unit divided by a time unit (seconds). Object K is undergoing non-constant acceleration. Object B is undergoing constant acceleration. Time (s) Velocity (m/s) Time (s) Velocity (m/s) And an object with constant velocity is NOT accelerating. I f an object is changing its velocity (whether constantly or varying), then it is accelerating. An object with constant acceleration should not be confused with an object with constant velocity. This is referred to as constant acceleration. A large acceleration represents a rapid CHANGE in velocity, but tells you nothing about the magnitude or direction of the velocity.Īn accelerating object can change its velocity by the same amount each second. If an object is NOT changing its velocity, then it is NOT accelerating.Īcceleration and velocity are different quantities. A person can be moving very fast yet not be accelerating. Summary PowerPoint (courtesy of Wayne County Schools)Īcceleration is defined as the rate which an object changes its velocity. The slope of the line on a velocity-time graph represents acceleration (change in velocity/change in time). The slope of the line on a position-time graph represents velocity (change in position/change in time). For a particle with uniform acceleration, velocity-time graph is a. When the v-t line has a NEGATIVE SLOPE and the velocity is also negative (-5m/s), the object is speeding up. Velocity Time Graph MakerAcceleration can be calculated by dividing the change in. When the v-t line has a NEGATIVE SLOPE, and the velocity is positive (5m/s), the object is slowing down. When the v-t line has a POSITIVE SLOPE and the velocity is negative (-5m/s), the object is slowing down. When the v-t line has a POSITIVE SLOPE, and the velocity is also positive (5m/s), the object is speeding up. How can you tell when an object is speeding up or slowing down? If the v-t graph has a negative slope, the object is undergoing acceleration in the NEGATIVE direction (not necessarily speeding up). You have to make sure that your v-t graph has a CLEAR negative component.Īcceleration: If the v-t graph has a positive slope, the object is undergoing acceleration in the POSITIVE direction (not necessarily speeding up). If the graph has a negative slope, then the object is undergoing acceleration in the negative direction (usually below the origin) If the graph has a positive slope, then the object is undergoing acceleration in the positive direction (usually above the origin) If an object is NOT moving = velocity is 0 A velocity-time (v-t) graph shows an object's velocity as a function of time. ![]()
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