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Falling Objects

Falling Objects. SNAP Guide. Read page 130; and answer all 7 questions on that page (‘net research may be required) Do Q1 on page 131 (‘net research may be required) Read page 132. Galileo:.

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Falling Objects

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  1. Falling Objects

  2. SNAP Guide • Read page 130; and answer all 7 questions on that page (‘net research may be required) • Do Q1 on page 131 (‘net research may be required) • Read page 132

  3. Galileo: • He gave a name to this force that seemed to“pull” objects towards Earth … the gravitational force, or GRAVITY! • Objects on Earth accelerate to the ground because of acceleration due to gravity • All free falling objects will fall at the same rate • This may appear different due to surface area and friction (due to air resistance)

  4. Galileo cont’d. • ag = g = acceleration due to gravity = 9.8 m/s2 (down), at sea level • For a falling object, velocity increases in magnitude by 9.8 m/s each second • This number is an average and can change slightly depending on where you are (relative to the center of the Earth)

  5. Calculating g • From a velocity-time graph of a free falling object

  6. Calculating g • From the time it takes for an object to fall • Example: • A ball is dropped from a height of 8.12 m and it takes 1.284523 s to hit the ground. What is the rate of acceleration?

  7. Another Example • An arrow is projected upwards from ground level at a velocity of 25.0 m/s. Find two different times where the arrow will have a velocity of 15.0 m/s.

  8. Practice • SNAP guide, pages 133 to 137, odd-numbered problems • Read page 137 and 149 • Do odd-numbered problems from pages 150 to 154

  9. Projectiles • Object that is shot / fired straight up, at some angle, or horizontally • We’ll examine: object launched off some height with only a horizontal velocity

  10. Projectile Motion Components • All projectiles have two components: vertical and horizontal • Vertical and horizontal components of the velocity are INDEPENDENT! The only thing linking them is TIME! • Horizontal velocity is constant (no acceleration)

  11. Horizontal Component • vx= dx / t • dxis the horizontal distance travelled • How does a horizontal component velocity vs. time graph look for a projectile?

  12. Vertical Component • Vertical velocity is changing (due to gravity!) • Initial vertical velocity is zero • Acceleration is 9.8 m/s2 downwards • Is down positive or negative? • Height of drop is d in equations: • vf2 = vo2 + 2ad • vf = vo + at • d = vot + ½ at2

  13. Example • A car travelling at 56 km/h drives off a 250 m high cliff. a) How long does it take to hit the ground? b) How far from the base of the cliff does it land? c) What is the vertical velocity when it hits the ground? d) What is the car’s horizontal velocity when it hits the ground?

  14. Practice • SNAP guide • Read pages 154 to 155 • Do odd-numbered questions on pages 156 & 157

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