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Physical Science

Physical Science. Mrs. Marsden. Chapter 1: Measuring Motion. 1. Reference Point – non moving objects. 2. Motion of an object – when an object changes position over time. 3. Speed depends on distance and time . 4. Speed – the distance an object moved over the time the motion took place.

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Physical Science

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  1. Physical Science Mrs. Marsden

  2. Chapter 1: Measuring Motion • 1. Reference Point – non moving objects. • 2. Motion of an object – when an object changes position over time. • 3. Speed depends on distance and time. • 4. Speed – the distance an object moved over the time the motion took place. • 5. Average speed (velocity) = • total distance / total time

  3. Chapter 1: Velocity • Direction Matters • Velocity is the speed of an object in a certain direction. • Acceleration is the rate at which velocity changes over time. • Objects accelerate if its speed, direction or both change • Acceleration = ∆v/ t = vf – vi / time

  4. Problems! Velocity = distance / time • What is the speed of a car traveling 70m in 15.9s? V = d / t = 70m / 15.9s = 4.40 m/s 2. What is the acceleration of a car that starts at rest and reaches a speed of 9m/s in 3s? a = vf – vi / time = (9 – 0) / 3 = 3 m/s2

  5. Unit Review! • t = seconds v = m/s • d = meter a = m/s2 3. What is the acceleration of a train car that has an initial velocity of 15 m/s and a final velocity of 10 m/s and travels for 2 seconds? A = (10 – 15) / 2 = -2.5 m/s2 (it is slowing down)

  6. 5.2 What is a Force? • A force is a push or a pull • Scientists use the SI unit, the Newton (N) • Forces Acting on objects • A push • A pull • Determine Net Force • Combine all forces acting on an object • Forces in the same direction • Forces in opposite direction 25 N 20 N 45 N, to the right 10 N 12 N 2 N, to the right

  7. Notes - Net Forces

  8. Notes - Balanced and Unbalanced Forces • Balanced Forces • Their Net Forces equal 0N • Unbalanced Forces • Causes objects to move, so it causes changes in speed, direction or both

  9. Notes – Friction: A force that opposes motion • Rough surfaces causes friction. • Friction – a force that opposes motion between two surfaces that are in contact. • Two factors: • Force of the surface • Roughness of the surface • Two types: • Kinetic • Static

  10. Notes – Friction: A force that opposes motion • Kinetic friction – “moving friction” • Ex: a potted plant sliding on a floor • Static Friction – “not moving” • The object does not move because the force fo static friction balances the force applied

  11. Notes – Friction: A force that opposes motion • Harmful or helpful? • Harmful = holes in your socks • Helpful = car tires push against the ground to move a car forward • Reducing friction • Sand wood • Ball bearings • Rub with oil for a slick surface

  12. 5.4 Gravity: A Force of Attraction • Gravity is a force of attraction between objects that is due to their masses • The effects of gravity on matter: • All matter has mass • Gravity results from mass • So, mass is a measure, matter in kg • So, force of gravity is related to mass of the objects

  13. Notes 5.4 Gravity: A Force of Attraction • Law of Universal Gravitation • Gravitational Force as mass • Gravitational Force as distance • Weight as a measure of Gravitational Force • Weight changes as gravitational force changes • Weight – measure of the gravitational force exerted on the object • Weight - measured in the Newtown (N)

  14. Gravity Calculations Gravity- A force that acts between any two masses. It’s an attractive force. It pulls objects together. Calculate gravity with the formula: Fg = m x g Example: What is your weight (Fg) on earth if your mass is 75kg? Fg= m x g = 75kg x 9.8 m/s2 = 735N

  15. What to study for Gravity Quiz • Your notes • Your Bellwork (green) • Your Gravity Problems • Re-read your guided reading on 5.4

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