course PHY201
Week 4 Quiz 1Richard Hogan
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September 1, 2007
A projectile leaves the edge of a table and, while traveling horizontally at a constant 37cm/s,
falls freely a distance of 149cm to the floor. If its vertical acceleration is 980 cm/s^2, how long
does it take to fall and how far does it travel in the horizontal direction during the fall?
Answer: If the balls rolls off of the table at a horizontal rate of 37cm/s, yet free falls like any
other object according to Galileo's theory 149cm, we can find out how far it will travel
horizontally and how long it will take for the object to fall vertically.
Vertical Motion:
vf^2 = v0^2 + 2a * ds
vf^2 = 0 + 2(980cm/s^2)(149cm) = 292040cm^2/s^2
vf = sqrt(292040cm^2/s^2) = 540.4cm/s
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vAve = (v0 + vf) / 2
vAve = (0cm/s + 540.4cm/s) / 2 = 270.2cm/s
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dt = ds/vAve = 149cm / 270.2cm/s = .55s
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Horizontal Motion:
ds = dt * vAve = .55s * 37cm/s = 20.35cm
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So after calculating the ball falls to the floor in 0.55 seconds and travel a horizontal distance
of 20.35cm."
Good solution. Keep up the good work.