Acceleration Physics 1-D Motion

Acceleration When velocity changes, we call that acceleration! There are 3 ways in which velocity can change: slowing down, speeding up, or changing direction.

Equation for Acceleration Acceleration = (final velocity-initial velocity) / time a= v/t

Slowing Down? When an object slows down, that can be called acceleration. ( + acc.) It is usually called deceleration( - acc.) It can also be called negative acceleration

Acceleration 3.1 Average and Instantaneous Acceleration Section Acceleration 3.1 Average and Instantaneous Acceleration The average acceleration of an object is the change in velocity during some measurable time interval divided by that time interval. Average acceleration is measured in m/s2. The change in velocity at an instant of time is called instantaneous acceleration.

Acceleration 3.1 Average and Instantaneous Acceleration Section Acceleration 3.1 Average and Instantaneous Acceleration The instantaneous acceleration of an object can be found by drawing a tangent line on the velocity-time graph at the point of time in which you are interested. The slope of this line is equal to the instantaneous acceleration.

Acceleration 3.1 Velocity and Acceleration Section Acceleration 3.1 Velocity and Acceleration Solve for acceleration at 1.0 s:

Acceleration 3.1 Velocity and Acceleration Section Acceleration 3.1 Velocity and Acceleration The slope of the line at 1.0 s is equal to the acceleration at that time.

Acceleration 3.1 Velocity and Acceleration Section Acceleration 3.1 Velocity and Acceleration Solve for acceleration at 5.0 s:

Acceleration 3.1 Velocity and Acceleration Section Acceleration 3.1 Velocity and Acceleration The slope of the line at 5.0 s is equal to the acceleration at that time.

Acceleration 3.1 Velocity and Acceleration Section Acceleration 3.1 Velocity and Acceleration The acceleration is not constant because it changes from 3.4 m/s2 to 0.03 m/s2 at 5.0 s. The acceleration is in the direction chosen to be positive because both values are positive.

Freefall Any object which is moving and being acted upon only by the force of gravity is said to be "in a state of free fall." Free-falling objects do not encounter air resistance.

Free Fall 3.3 Acceleration Due to Gravity Section Free Fall 3.3 Acceleration Due to Gravity After a lot of observation, Galileo concluded that, neglecting the effect of the air, all objects in free fall had the same acceleration. It didn’t matter what they were made of, how much they weighed, what height they were dropped from, or whether they were dropped or thrown. The acceleration of falling objects, given a special symbol, g, is equal to 9.80 m/s2. The acceleration due to gravity is the acceleration of an object in free fall that results from the influence of Earth’s gravity.

Falling Objects Gravity is the force of attraction between any 2 objects, depending on their mass and distance apart g= acceleration due to gravity ALL objects free-fall at -9.8 m/s2 Negative sign because objects are accelerating toward the center of the earth..

Freefall Equations To determine how fast an object is travelling: vf = g * t To determine how far a free-fall object travels: d = 0.5 * g * t2

Freefall on Graphs

                        

Cause a change in an object’s velocity Cause acceleration Forces Cause a change in an object’s velocity Cause acceleration

Balanced vs. Unbalanced Balanced: Forces combine so the total force acting on an object is 0. Unbalanced: Forces produce an acceleration

A force that opposes motion Friction A force that opposes motion Friction depends on the surfaces in contact

Gravity A force between two objects depending on the object’s mass and distance apart