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Aim: How do we use Newton’s equation of Motion to explain the motion of a projectile launched upwards?
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Free Fall All bodies accelerate downwards at -9.8 m/s2 on earth regardless of mass (in the absence of air resistance). On the moon, the acceleration due to gravity is m/s2 . Since there is no air resistance on the moon, a penny and feather will hit the ground at the same time.
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Projectiles Fired Upwards
We know three things about projectiles thrown upwards: (Assume no air resistance) The velocity of the projectile at its maximum height is equal to 0.
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Projectiles Fired Upwards
2. The time it takes the object to rise is equal to the time it takes the object to fall the same amount of distance.
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Projectiles Fired Upwards
3. The velocity with which the projectile is launched upwards will be equal in magnitude to the velocity of the projectile when it hits the ground.
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Projectiles Fired Upwards
Note: When solving projectile motion problems in which the projectile is fired upwards, it is especially important that we make acceleration vector negative (-9.8) and the initial velocity vector is positive.
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Example -Firing projectiles upward
An arrow is fired upwards with a velocity of 15 m/s. How high does the arrow rise? How long does it take the arrow to reach maximum height? What is the total flight time? a) m b) 1.5 s c) 3s
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Trampoline Example A boy jumps on a trampoline with an initial velocity of 5.0 m/s. How high does the boy jump? What is the total time that boy is in air for? a) m b) 1s
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Rocket Stomper Assume the rocket is fired straight upwards.
If the rocket reaches a maximum height of 12 m, What is the initial velocity with which it was launched? How long is the rocket in the air for? a) 15.3 m/s b)3.12 a
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Design the Following Experiment
The only equipment you have is a timer (stopwatch). Design an experiment to determine how high the bottle rocket went. State all relevant equations you will use. Draw a sketch.
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Problem A Gwendolyn throws her crystal vase vertically upwards with an initial velocity of 26.2 m/s. Determine the height to which the vase will rise above its initial height.
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Problem B With what speed must an object be thrown to reach a height of 91.5 m (equivalent to one football field)? Assume negligible air resistance. How long will object remain in air for?
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Michael Jordan-Problem C
Michael Jordan was said to have a hang-time of 3.0 seconds (at least according to a popular NIKE commercial). Use kinematic equations to determine the height to which MJ could leap if he was wearing NIKE shoes and had a hang-time of 3.0 seconds.
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Problem D-Hot Air Balloon
A tourist takes a trip in a hot air balloon. The hot air balloon is ascending (moving up) at a velocity of 4 m·s−1. He accidentally drops his camera over the side of the balloon's basket, at a height of 20 m. Calculate the velocity with which the camera hits the ground.
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Problem E A ball is thrown upwards with an initial velocity of 10 m·s−1. 1. Determine the maximum height reached above the thrower's hand. 2. Determine the time it takes the ball to reach its maximum height.
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