The discussion centers on the validity of kinematic equations, specifically the SUVAT equations, which are applicable under conditions of constant acceleration. Participants clarify that these equations are not universally true as they rely on specific assumptions, such as negligible air resistance and frictionless surfaces. For instance, the equation Distance = Speed × Time fails when acceleration is not constant, such as in projectile motion or when air resistance is significant. The conversation emphasizes that while the SUVAT equations are reliable within their defined parameters, they can be misapplied if the conditions are not met.
PREREQUISITESStudents in physics, educators teaching kinematics, and anyone interested in understanding the limitations and applications of motion equations in various contexts.
i wanted to say the equations that are not always fulfilled in the kinematic.etotheipi said:What do you mean by "true"? There are many equations which have a realm of validity, i.e. that rely on specific assumptions, if that's what you're asking.
Any equation is only valid in specified circumstances. Even then, some are only approximations valid over a certain range.Lucho G said:i wanted to say the equations that are not always fulfilled in the kinematic.
Let's assume :Lucho G said:Homework Statement:: Are there kinematic equations that are not always true? If so, which ones and in what cases?
Here is one. Distance = Speed × Time is not true in the case when the object accelerates. Can you think of another one? You have already received some hints.Lucho G said:Homework Statement:: Are there kinematic equations that are not always true? If so, which ones and in what cases?
Relevant Equations:: Cinematica
please I need to clarify this question
thanks sincerely
Luis
You get maximum range in projectile motion regardless of difference between launch and landing level if the initial velocity and the final velocity vectors are perpendicular. The 45o projection angle is a special case of that when the vertical velocity component just changes sign upon landing. You can find the details here.maxwells_demon said:the most prominent i can think about is the "max range" projectile equations. all of them assume 45 degrees as the optimal angle for launch. however that may not be true if the launch level and the landing level are different. which means all the shortcut equations related to this special case "burn and die".
All? Counter-example: Simple harmonic motion.PhDeezNutz said:All the kinematics equations you are likely to be exposed to at the freshmen and sophomore level assume constant acceleration.
Throw constant acceleration out the window and the formulas are no longer valid (Obviously).
kuruman said:You get maximum range in projectile motion regardless of difference between launch and landing level if the initial velocity and the final velocity vectors are perpendicular. The 45o projection angle is a special case of that when the vertical velocity component just changes sign upon landing. You can find the details here.
Specifically, the SUVAT equations.PhDeezNutz said:All the kinematics equations you are likely to be exposed to at the freshmen and sophomore level assume constant acceleration.
kuruman said:All? Counter-example: Simple harmonic motion.
haruspex said:Specifically, the SUVAT equations.
But I see it as wrong to say the equations are not always 'true'. As I posted, all equations come with specifications of what the variables mean and under what conditions they apply; it's a package. The SUVAT equations are always true, but they can be misused.
For SUVAT it's not just that acceleration is constant, you also need to ensure displacement, velocity and acceleration are all being measured in the same straight line.