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Understanding Motion: Speed, Velocity, and Forces

This chapter in physical science explores the essential concepts of motion, including reference points, speed, velocity, and acceleration. It explains how speed is determined by distance and time, while velocity incorporates direction. The chapter illustrates the significance of acceleration as the rate of change in velocity. Additionally, it covers forces, including gravitational force and friction, and the differences between balanced and unbalanced forces. Through problem-solving examples, students will learn to calculate speed, acceleration, and understand the implications of forces acting on objects in motion.

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Understanding Motion: Speed, Velocity, and Forces

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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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