KINEMATICS EQUATIONS AND GRAVITY Gravity Does gravity ever

KINEMATICS EQUATIONS AND GRAVITY

Gravity � Does � gravity ever turn off? NO Does gravity affect everything in the same way? YES! � Why does the book hit before the paper? Air Resistance slows down the paper- but that doesn’t change the fact that gravity is still pulling it down. � � If I throw a ball into the air, is gravity affecting it? YES. My hand speeds the ball up, but as soon as it leaves my hand, it begins to slow down. When the ball reaches it’s highest point, it briefly comes to a stop before changing direction. What is it’s velocity? Is it accelerating? zero Yes! Gravity!

Acceleration Units acceleration= velocity time SI units = m/s/s =m s 2 = distance/time

Acceleration direction � (+) means forward/up, � (-) means backward/down +v +a Forward, speeding up -v -a Backward, speeding up +v -a Forward, slowing down -v Backward, slowing down +a

Thinking Questions � If a ball falls off of a shelf and you calculate the velocity right before it hits the floor, will the velocity be + or -? NEGATIVE… moving down

Thinking Questions � If you toss a ball in the air, is it’s initial velocity + or -? Positive… moving up

Thinking Questions � If you toss a ball in the air, as it rises, will it’s acceleration be + or -? NEGATIVE… moving upward, but slowing

GRAVITY g (on earth) = -9. 81 m/s 2

Kinematics Equations: Equation a = v f - vi Δt For use when you know/need: a vi vf t Unknown: d a = vf 2 - vi 2 2(Δd) a vi vf d t Δd = vi t + 12 at 2 a vi d t vf