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Published byGloria Roberts Modified over 5 years ago

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**The four kinematic equations which describe an object's motion are:**

There are a variety of symbols used in the above equations and each symbol has a specific meaning. d – the displacement of the object. (we use “x” & will also use “y”) t – the time for which the object moved. a – the acceleration of the object. vi – the initial velocity of the object. vf – the final velocity of the object.

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**The four kinematic equations which describe an object's motion are:**

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**Position Of Free Falling Object At Regular Time Intervals**

The position of the free-falling object at regular time intervals, every 1 second, is shown. The fact that the distance which the ball travels every interval of time is increasing is a sure sign that the ball is speeding up as it falls downward.

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**Velocity Of Free Falling Object At Regular Time Intervals**

Assuming that the position of a free-falling ball dropped from a position of rest is shown every 1 second, the velocity of the ball will be shown to increase

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**Velocity Of Free Falling Object At Regular Time Intervals**

Observe that the line on the graph is curved. A curved line on a position vs. time graph signifies an accelerated motion. Since a free-falling object is undergoing an acceleration of g = 10 m/s/s (approximate value), you would expect that its position-time graph would be curved. A closer look at the position-time graph reveals that the object starts with a small velocity (slow) and finishes with a large velocity (fast). Since the slope of any position vs. time graph is the velocity of the object, the initial small slope indicates a small initial velocity and the final large slope indicates a large final velocity. Last, but not least, the negative slope of the line indicates a negative (i.e., downward) velocity.

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**Velocity Of Free Falling Object At Regular Time Intervals**

look at the velocity-time graph reveals that the object starts with a zero velocity (starts from rest) and finishes with a large, negative velocity; that is, the object is moving in the negative direction and speeding up. An object which is moving in the negative direction and speeding up is said to have a negative acceleration This analysis of the slope on the graph is consistent with the motion of a free-falling object – an object moving with a constant acceleration of 10 m/s/s in the downward direction.

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How Fast? The velocity of a free-falling object which has been dropped from a position of rest is dependent upon the length of time for which it has fallen. The formula for determining the velocity of a falling object after a time of t seconds is: vf = vi + (-g)t where g is the acceleration of gravity (approximately -10 m/s/s on Earth; its exact value is m/s/s). The equation above can be used to calculate the velocity of the object after a given amount of time.

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**How FAST ? Example t = 6 s vf = (0 m/s) + (-10 m/s2) (6 s) = - 60 m/s**

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How Far?

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How FAR ? Example The NEGATIVE displacement, indicates that the object is falling DOWN

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