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Wednesday – November 7. Review Exam on Friday. REVIEW. You are allowed on flash card. I will NOT provide formulas. What is the resultant of a pair of forces 100N upward and 75N downwards? 25N up. Why is speed scalar and velocity vector? Speed is only a number.

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## Wednesday – November 7

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**Wednesday – November 7**• Review • Exam on Friday**REVIEW**• You are allowed on flash card. • I will NOT provide formulas.**What is the resultant of a pair of forces 100N upward and**75N downwards? 25N up**Why is speed scalar and velocity vector?**Speed is only a number. Velocity is speed in a given direction.**What is the end point for:**45° for 3 blocks, S for 7**Calculate the resultant for the following:**8m east, 2m north, 6 m west 22+22 = √8 = 2.9m NE**A ball is dropped from a 60m high building. How far will it**have fallen after 3.0 seconds? y = ½ gt2 4.8m/s2 x 9s2 = 44.1m**In the absence of air resistance, why does the horizontal**component of velocity for a projectile remain constant? No other forces are involved.**A bird flies at 20km/h. How long does it take to fly 400km?**400km/ 20km/hr = 20hours**A rock is thrown at a target 40m away. It hits the target**in 4.0 seconds. What is the speed of the rock? 40m/4.0 seconds = 10m/s**A stone is dropped from a bridge and hits the ground after**4.0 seconds. How high is the cliff? y = ½ gt2 4.8m/s2 x 4.0s2 = 78.4m**A salmon jumps up a waterfall to return home to spawn. The**waterfall is 2.0m high. What minimum speed must the fish meet to jump the waterfall? vf2 = vyo2 + 2a ∙ d = 6.26m/s**What is the resultant path of a ship traveling north at 8m/s**if the tide is pushing at 2m/s east. What is the angle? 82m/s + 22m/s = √68m2/s2= 8.2m/s 8/2 tan-1 = 76°**A rock is dropped and hits bottom 5 seconds later. What is**its velocity just before it hits bottom. vy = vyo + ayt 9.8m/s2 x 5 s = 49m/s What is the height of the cliff? y = ½ gt2 = 4.9m/s2 x 25 s2 = 122.5m**A rock is thrown from a cliff at 20m/s. What is the**horizontal velocity after 2.0 seconds? 20m/s What is its vertical velocity in 2.0s? y = ayt 9.8m/s2 x 2.0 s = 19.8m/s**A rock is thrown from a cliff at 20m/s. What is its**horizontal displacement after 3.0s? x = vxi t = 20m/s x 3.0s = 60m**A man shoots a gun at 2m above ground. The bullet is fired**and hits the ground 1000m away. What vertical velocity did the bullet hit the ground? • vfy2 = voy2 + 2a x d • 2(9.8m/s2) x 2m = vfy2 • √39.2m2/s2 = 6.26m/s**A ball is projected horizontally from a point 245m above the**ground. How long does it take to reach the ground? • y = ½ gt2 • t2 = y ÷ ½ g • 245m ÷ 4.9m/s2 = √50s2 • = 7.07 seconds**A ball is projected horizontally from a point 245m above the**ground. How long does it take to reach the ground? = 7 seconds • If the ball strikes 49m horizontally from the point of projection, what is the horizontal velocity? • v = d/t 49m/7s = 7m/s**A projectile is shot upward at a 60° angle from the ground**at 60m/s. What is the vertical component of velocity? • y = 60m/s (sin 60°) = 52m/s • What is its horizontal component of velocity? • vx= v (cosӨ) • vx = 60m/s (cos 60°) = 30m/s • How far in the x direction has it gone in 3 seconds? • x = vt 30m/s x 3 seconds = 90m

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