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course Phy 201
3/12/11 around 7:52
A projectile leaves the edge of a table and falls freely a distance of 123 cm to the floor. It travels a horizontal distance of 17.7 cm during its fall. How long does it take to fall and what is its horizontal velocity during the fall?
V0= 0cm/s `ds= 123cm a= 9.8m/s/s `dt= ?
vf= sqrt (0cm/s^2 + 2 * 9.8m/s/s * 123cm) = 49.1cm/s
(0cm/s + 49.1cm/s)/2 = 24.55cm/s vAve 24.55cm/s= 123cm/`dt = 5.01sec to fall
vf^2= v0^2 + 2 a `ds
Horizontal velocity is constant, therefore vave= 17.7cm/ 5.01sec = 3.5cm/s"
Self-critique (if necessary):
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#$&*
@& Your reasoning is great and would have worked perfectly, but you used m/s/s for acceleration and cm for displacement when calculating the final velocity. That won't work. Work the problem in meters, in which case `ds = 1.23 m, or in cm, in which case g = 980 cm/s^2.
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