One of the most important applications of physics is the ability to predict the future movement of an object based on past information about the object. This deterministic view of physics allows one to predict the motion of all kinds of objects, like space ships, vehicles, ballistics and any other body in motion. The study of the motion of bodies is called kinematics, and an important variable in kinematic equations is time, which signifies that the motion of a body changes with time. Finding the time in kinematic equations can be completed in a few short steps.
Write down any known quantities given to you in the question. For example, assume the question is asking you to find the time it takes for an object to travel 10 meters (m) if it starts moving with a velocity of 2 meters per second (m/s). In this question, the known quantities are 2 meters for the initial position, and 10 meters for the displacement of the object.
Find the appropriate kinematic equation, given the information provided to you. For the information given in this question, the appropriate kinematic equation is
xf = x0 + vt,
where xf is the final position, x0 is the initial position, v is the velocity and t is the time.
Plug the appropriate values into the equation. In the example given, the displacement can be written as the initial position subtracted from the final position. Therefore, the equation simplifies to
(xf - x0) = vt
d = vt.
Substituting values into this equation gives
10 (m) = 2 (m/s) t.
Solve the kinematic equation for the time. In this example, solving the equation
10 (m) = 2 (m/s) t
t = 10 (m) / 2 (m/s)
t = 5 seconds (s)
Therefore, the time in this kinematic equation is 5 s.
- Physics Classroom: Kinematic Equations
- HyperPhysics: Description of Motion in One Dimension
- "Physics for Scientists and Engineers: 6th Edition"; Raymond A. Serway and John W. Jewett; 2004
- Photo Credit Jupiterimages/Photos.com/Getty Images
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