Chapter 3 Linear Motion

1. Chapter 3Linear Motion Notes

2. Symbols • velocity v • distance d • Acceleration a • Gravitational g acceleration

3. Formulas • v=d • ∆v= vf -vo • a=∆v t • v = at • v=gt • d=1 gt2 2 • t = 2d g

4. Vocab. • ∆means change read as “delta” Rate- • how fast something happens, or how much something ∆’s per unit of time a ∆ in a quantity divided by time it takes for ∆ to occur a quantity divided by time linear motion- • motion along a straight-line path relative- • regarded in relation to something else depends on pt of view, or frame of reference sometimes referred to as “w/ respect to "Motion is relative: “moves with respect to...” Motion will be relative to surface of earth 2 types of quantities: • 1. Scalar quantity-has magnitude (size) only • 2. Vector quantity-has both magnitude (size) & direction (N, S, E, or W)

5. Vocab constant velocity- • obj. doesn’t move faster or slower speed and direction does not change constant direction-motion remains in st. line changing velocity- • either speed or direction (or both) is changing can have constant speed but be going around a curve • ∆v = vf - vo • Vf = final velocity • vo = original velocity

6. Try These… ? A car traveling at 55mph speeds up to 70mph north. What is its change in velocity? ? A car traveling South at 55 m/s hits the brakes screeching to a stop. What is its ∆ in velocity? A=15mph North A=55m/s South

7. Vocab Speed • how fast something is moving • average speed = distance traveled/elapsed time • distance covered per time • slash symbol (/ ) means “per” means divided by instantaneous speed- • speed at an instant of time rate at wh/ dist. is traveled read by car’s speedometer average speed- • path distance divided by time interval displacement- • how far something travels in a given direction is a vector quantity

8. Vocab vector quantity- has both magnitude (size) & direction • examples: 1. velocity 250 m/s north 2. displacement (distance in a given direction) 30m East 3. acceleration 10 m/s/s downward towards earth’s surface velocity- speed together w/ direction of motion how fast and in what direction velocity is a vector quantity velocity = distance elapsed time

9. Vocab acceleration- rate at wh/ velocity ∆’s. This ∆may be in magnitude, direction or both 4 how the velocity is changingwith respect to time how quickly velocity ∆’s acc. is a rate of a rate acceleration (acc)= change in velocity time interval a = ∆v = vf-vo t t ?A car speeds up from 40m/ s to 50m/ s in 2 seconds. What is its acceleration? A= 5m/s/s

10. Vocab deceleration- • the final velocity of a moving object is smaller than its initial velocity • object is slowing down • aka: negative acceleration • neg. acc is expressed w/ a negative sign preceding the magnitude ?What is the acceleration of a car that goes from 60m/s to 45m/s in 5 seconds? Car: 3 controls used to ∆acceleration • 1. gas pedal (accelerator) -used to increase speed • 2. brake-used to decrease speed • 3. steering wheel-used to change the direction acceleration a = ∆v v = at t ? What is the velocity after 5 seconds of elapsed time for a car that accelerates at 2 m/s2 from a position of rest? A=-3m/s/s A=10m/s

11. Vocab free fall- • motion under the influence of gravitational force only movement of an object in response to a gravitational force • (no other forces acting on object) • freely falling objects are affected only by gravity • acceleration due to gravity is represented by g • the velocity increases by 10 m/ s for each successive second of fall • g = 10 m/s/s • free fall velocity: v = gt

12. ? What will be the velocity of a ball thro wn straight up with an initial velocity of 30 m/s after 1s? Try it • ? What is the instantaneous velocity of a falling object after 1s? • What is the instantaneous velocity of a falling object after 2s? • ? What is the instantaneous velocity of a falling object after 3s? • ? What is the instantaneous velocity of a falling object after 6.3 s? • By how much (m/s) did the velocity of the falling object ∆ for each successive second? • ? What will be the velocity of a ball thrown straight up with an initial velocity of 30 m/s after 1s? after 2s? after 3s? • What is its acceleration after each second? after 2s? after 3s? What is its acceleration after each second?

13. Distance of Free Fall if you measure the distance fallen each second.... the distance is not the same the distance traveled increases with each successive second of freefall • d =1 gt2 2

14. Try it ? How far will a freely falling ball travel after 1s? ? How far will a free falling ball travel after 2s? ? How far will a free falling ball travel after 3s? ? How far will a free falling ball travel after 5s? ? How fast initially was a ball traveling if thrown straight upward and it takes 3 seconds to reach the top (apex)? ? How fast initially was a ball traveling if thrown straight upward and it takes 8 seconds to go up and return to the thrower’s hand? ? What velocity is needed to throw a ball straight up and have it return 10 s later?