Kinematics

 Kinematics and the Coin Toss

 Solutions

Q1: Sketch the path of this imaginary coin, including a definition of coordinates. Label the following points on your sketch.

 Point 1 The coin has just left your hand moving upwards Point 2 The coin is about 1/4 of the way up to the top of its path Point 3 The coin is about 3/4 of the way up to the top of its path Point 4 The coin is exactly at its maximum height of about 2.5m Point 5 The coin is about 1/4 of the way down from the top of its path Point 6 The coin is about 3/4 of the way down from the top of its path Point 7 The coin is just above your hand and is about to be caught

Q2: Assume upwards displacement is positive. Indicate the following points on your sketches. (In some cases there may be none, or more than one correct point. When this is so, explain in words.)

 Point A Maximum displacement of the coin Point B Zero displacement of the coin Point C Minimum displacement of the coin Point D Maximum velocity of the coin Point E Zero velocity of the coin Point F Minimum velocity of the coin Point G Maximum acceleration of the coin Point H Zero acceleration of the coin Point I Minimum acceleration of the coin

Q3: From your observations in Q2, prepare three sketch graphs: position vs. t, velocity vs. t and acceleration vs. t for one complete toss of the coin. Align the graphs in a colunm so that you can readily read the x,v and a values for the same time.

Q4: In your own words, describe how the position of the coin changes with respect to time during the toss.

The zero frame of reference is your hand going up in the positive direction. The distance increases until it reaches a maximum height, then the distance decreases until it reaches your hand at zero.

Q5: In your own words, describe how the velocity of the coin changes with resect to time during the toss.

The positive velocity occurs the instant the coin leaves our hand. It immediately begins slowing up until its upward velocity becomes zero at the maximum height. At this instant it begins to fall and its velocity increase in a negative direction. The velocity reaches its maximum negative value the instant before it touches your hand.

Q6: In your own words, desribe how the acceleration of the coin changes with respect to time during the toss.

The acceleration never changes, its direction is downward at -9.8m/s 2

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