Motion The graph describes an object’s motion during four time intervals. The intervals are labeled A–B, B–C, C–D, and D–E. Describes the object’s motion during each of the four time intervals.

Motion A–B During this interval the object was at rest. B–C During this interval the object was moving with a constant velocity in the positive direction. C–D During this interval the object was at rest. D–E During this interval the object had constant acceleration (does velocity change?) in the negative direction.

Motion The graph describes an object’s motion during four time intervals. The intervals are labeled A–B, B–C, C–D, and D–E. Describe the object’s motion during each of the four time intervals.

Motion A–B During this interval the object was at rest. B–C During this interval the object was moving with a constant velocity in the forward (or positive) direction. C–D During this interval the object was at rest. D–E During this interval the object had constant acceleration in the negative direction.

Problems 1. Calculate the speed over OA AB and BC 5, 0, 3.75m

2. Calculate (a)the acceleration over OA, AB and BC (b) the total distance traveled in the 12 s 5m/s2, 0, 3.75m/s2, 127.5m

Acceleration Due to Gravity Every object on the earth experiences a common force: the force due to gravity. This force is always directed toward the center of the earth (downward). The acceleration due to gravity is relatively constant near the Earth’s surface. Earth W g

Gravitational Acceleration In a vacuum, all objects fall with same acceleration. Equations for constant acceleration apply as usual. Near the Earth’s surface: a = g = 9.80 m/s2 or 32 ft/s2 Directed downward (usually negative).

Experimental Determination of Gravitational Acceleration. y Dt The apparatus consists of a device which measures the time required for a ball to fall a given distance. Suppose the height is 1.20 m and the drop time is recorded as 0.650 s. What is the acceleration due to gravity?

Experimental Determination of Gravity (y0 = 0; y = -1.20 m) Dt y = -1.20 m; t = 0.495 s + Acceleration of Gravity: W Acceleration a is negative because force W is negative.

Sign Convention: A Ball Thrown Vertically Upward Displacement is positive (+) or negative (-) based on LOCATION. v = - UP = + v = - a = - y = 0 y = 0 Release Point Velocity is positive (+) or negative (-) based on direction of motion. y = -Negative v= -Negative a = - Acceleration is (+) or (-) based on direction of force (weight). Tippens

a = - a = - a = - a = - y = + v = 0 v = - y = + v = + y = + v = - UP = + a = - y = 0 Tippens

Same Problem Solving Strategy Except a = g: Draw and label sketch of problem. Indicate + direction and force direction. List givens and state what is to be found. Given: ____, _____, a = - 9.8 m/s2 Find: ____, _____ Select equation containing one and not the other of the unknown quantities, and solve for the unknown.

Thrown upward The motion may be symmetrical Then tup = tdown Then v = -vo The motion may not be symmetrical Break the motion into various parts Generally up and down