What is physics exactly? The branch of science concerned with the nature and properties of matter and energy. The study of the physical world Includes mechanics, heat, light and other radiation, sound, electricity, magnetism, and the structure of atoms
All objects “fall” at same rate near the surface of the earth, & in the absence of friction Objects will fall at constant acceleration (at the rate of acceleration due to gravity) By “fall”, we are referring to the rate at which velocity changes And I’m free…..free falling!
SI units: ay = g = -9.81 m/s2 The velocity of an object changes 9.81 m/s every second. English units: ay = g = -32.2 ft/s2 The velocity of an object changes 32.2 m/s every second. Acceleration due to gravity
Acceleration due to gravity
It NEVER ceases to exist It ALWAYS works DOWN It is NEVER zero Acceleration due to gravity
For vertical motion, we use the same kinematic equations as before: In your book: xi, xf, Δx become yi, yf, Δy In your book: Acceleration (a) is g Analyzing falling objects using kinematic equations
Negative & positive signs are VERY important in vertical motion MUST be consistent G is negative Vertical downward displacement away from origin is negative Vertical upward displacement away from origin is positive Acceleration due to gravity
A ball is dropped from a tower 70.0 m high. If we neglect air friction, determine how far the ball has fallen after: 1.00 s 2.00 s 3.00 s Problem Solving Strategy: Identify knowns: Xi yi Xi Yf Vi Vf a g t Choose an equation Plug in values to solve the problem Example: xf = xi + vit + 0.5at2 yf= yi+ vit + 0.5gt2 yf =0 + 0+ 0.5(-9.81)t2 yf at 1.00 s = -4.90 m yf at 2.00 s = -19.6 m yf at 3.00 s = -44.1 m