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Projectile Motion
Independence of Motion in 2 Dimensions
Horizontally: Projectiles move with constant velocity.
Vertically: Projectiles accelerate with a constant rate of -9.80 m/s2 or -32.2 ft/s2
How to solve Projectile Problems:
1) Divide the problem into a vertical and horizontal problem.
2) The vertical problem is exactly like if the object was dropped or thrown straight up.
Use the three long equations and a = -9.80 m/s2 The horizontal problem is just like
solving a constant velocity problem: v = d / t
3) Find the time the object was in the air.
4) Both the horizontal and vertical components are linked by time. Use the time to find
what the question is asking.
A stone is thrown horizontally at 15 m/s from the top of
a cliff that is 44 m high. A) How far from the base of
the cliff does the stone hit the ground. B) How fast is it
moving the instant before it hits the ground.
Someone threw a ball horizontally from a tower 50.0 m.
tall. It hit his foot, 142.8 m away from the base of the
tower, and killed them instantly. There were two people
on that tower at the time: Randy Johnson and this guy.
Who should the state prosecute?
A 7mm Rem. Magnum (muzzle vel = 2840 fps
or________) is shot at an incline of 30 deg. Neglecting
air resistance: A) How high does the bullet go. B) How
far does the bullet go?
How far will a bullet really go?
A Classic Demo:
Matt Kenseth rounds turn 3 (radius 450. ft =
500. m) at Lowe’s Motor Speedway at
1.50 x 102 mph (67.1 m/s). The mass of him
and his car is 1620 kg. Find the centripital
acceleration on his car.
Find the centripetal force on his
car.
Find the minimum coefficient of friction
between the tires and the road such that he
can take the curve sans skidding out.
Assume the corners aren’t banked.
A 13.0 g rubber stopper is attached to a 0.93 m string. The
stopper is swung in a horizontal circle, making one revolution
in 1.18 s. Find the tension force exerted by the string on the
stopper.
An Audi R- 8 creates enough downforce at 150.0 mph to drive upside down. The
typical R – 8 weighs 1980 lbs. How much faster can an R – 8 take a 300.0 m radius
turn than a car of same weight & tires that creates no downforce? μ = .800