Forces and Motion Forces can create changes in

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Forces and Motion • Forces can create changes in motion (acceleration) • Deceleration is

Forces and Motion • Forces can create changes in motion (acceleration) • Deceleration is negative acceleration

Motion can be described as • a change in an object’s position • Average

Motion can be described as • a change in an object’s position • Average velocity (speed) is the change of position of an object over time

Velocity Graphs V = distance time • Velocity (v) is the slope (rise over

Velocity Graphs V = distance time • Velocity (v) is the slope (rise over run) of a position (d) vs. time (t) graph

40 The diagram represents the total travel of a teacher on a Saturday. Which

40 The diagram represents the total travel of a teacher on a Saturday. Which part of the trip is made at the greatest average speed? FQ How do we work this one? GR Calculate v = d/t for each segment. HS J T

Acceleration Graphs • Acceleration (a) is the slope of a velocity (v) vs. time

Acceleration Graphs • Acceleration (a) is the slope of a velocity (v) vs. time (t) graph • Plotted on a distance vs. time graph, acceleration is an exponential curve

Acceleration is a change in an objects velocity (speed or direction) • When an

Acceleration is a change in an objects velocity (speed or direction) • When an object’s speed changes over time it is accelerating (or decelerating) • A = vfinal – vinitial time • Units for acceleration m/s/s or m/s 2

Definition of a Force • A Force is a push or a pull

Definition of a Force • A Force is a push or a pull

Balanced Force • A force that produces no change in an object’s motion because

Balanced Force • A force that produces no change in an object’s motion because it is balanced by an equal, opposite force.

4 The picture shows the position of a ball every 0. 25 second on

4 The picture shows the position of a ball every 0. 25 second on a photogram. Using a ruler, determine the velocity of the ball. F 3. 5 cm/s G 10. 5 cm/s H 14. 0 cm/s J 28. 0 cm/s

Use the ruler on the side of the chart and the equation for velocity.

Use the ruler on the side of the chart and the equation for velocity. The answer was H. Measure from the center of ball 1 to the center of ball 2 and multiply by 4.

Unbalanced Forces Are forces that results in an object’s motion being changed. +

Unbalanced Forces Are forces that results in an object’s motion being changed. +

Friction A force that acts in a direction opposite to the motion of two

Friction A force that acts in a direction opposite to the motion of two surfaces in contact with each other.

Friction causes an object to slow down and stop. Since the amount of energy

Friction causes an object to slow down and stop. Since the amount of energy stays constant, the energy becomes heat.

Universal Law of Gravitation All objects in the universe attract each other by the

Universal Law of Gravitation All objects in the universe attract each other by the force of gravity

Universal Law of Gravitation 1) the mass of the object doing the pulling, and

Universal Law of Gravitation 1) the mass of the object doing the pulling, and Gravity varies depending on two factors: 2) the distance from the center of that object

On Earth gravity = 9. 8 m/s/s • For every second that an object

On Earth gravity = 9. 8 m/s/s • For every second that an object falls its speed increases by 9. 8 m/s

Weight= Mass (m) X gravity (g) • • Weight Unit of mass = kg

Weight= Mass (m) X gravity (g) • • Weight Unit of mass = kg Unit of acceleration = m/s/s Unit of weight = Newton 1 Newton= about ¼ pound