Motion in One Dimension Velocity and Acceleration

Describe the motion of the buggy.

Rate This is a key term, one that you need to be sure to master in order to fully understand physics!

How does the motion of these 2 buggies compare? What terms do we need to use? Is there a rate involved with their motion?

Displacement A change in position (DX)

Distance (d) How far an object travels

Positive Displacement (s) Moving in the positive direction as determined by your frame of reference

Negative Displacement (-s) Moving in the negative direction as established by your frame of reference

Speed Distance traveled per unit of time V=d/t Units: m/s Scalar quantity (size only)

Velocity Displacement an object experiences per unit of time V=s/Dt Units: m/s (with a direction) Vector quantity (size and direction)

Sample #1 Heather and Matthew take 34 minutes to walk eastward along a straight road to a store 2.0 km away. What is their average velocity in m/s? 0.98 m/s eastward

Sample #2 Simpson drives his car with an average velocity of 24 m/s toward the east. How long will it take him to drive 560 km on a perfectly straight highway? 6.5 hours

Sample #3 Eugeneville is 75.0 km due south of Salemtown. If Joe rides from Salemtown to Eugeneville on his bike in 6.00 hours, what is his average velocity in m/s? 3.47 m/s

Sample #4 A bus traveled south along a straight path for 3.2 hours with an average velocity of 88 km/h, stopped for 20.0 min, then traveled south for 2.8 hours with an average velocity of 75 km/h. What is the average velocity for the total trip? What is the displacement for the total trip? 78 km/h south, 490 km south

How does the motion of the battery car and buggy compare? What terms do we need to use? Is there a rate involved with their motion?

Acceleration Change in velocity per unit of time a= Dv/Dt Units: m/s2 Vector quantity (size and direction)

Sample #5 When the shuttle bus comes to a sudden stop to avoid hitting a dog, it slows from 9.00 m/s to 0.00 m/s in 1.50 s. What is the average acceleration of the bus? -6.00 m/s2

Sample #6 With an average acceleration of -0.50 m/s2, how long will it take a cyclist to bring a bicycle with an initial velocity of +13.5 m/s to a complete stop? 27 s

Is constant acceleration possible?

Uniform Acceleration s = ½ (Vi + Vf)Dt No info on: a Note card Needed! s = ½ (Vi + Vf)Dt No info on: a Vf = Vi + aDt No info on: s s = ViDt + 1/2aDt2 No info on: Vf Vf2 = Vi2 + 2as No info on: Dt

Vi a Motion + Speeding up - Slowing down - or + Constant velocity Speeding up from rest Remaining at rest

Sample #7 A car accelerates uniformly from rest to a speed of 23.7 km/h in 6.5 s. Find the distance the car travels during this time. 21 m

Sample #8 When Maggie applies the brakes of her car, the car slows uniformly from 15.00 m/s to 0.00 m/s in 2.50 s. How many meters before a stop sign must she apply her brakes in order to stop at the light? 18.8 m

Sample #9 A car with an initial speed of 23.7 km/h accelerates at a uniform rate of 0.92 m/s2 for 3.6 s. Find the final speed and the displacement of the car during this time. 36 km/h (9.9 m/s), +0.030 km

Sample #10 A driver of a car traveling at -15 m/s applies the brakes, causing a uniform acceleration of +2.0 m/s2. If the brakes are applied for 2.5 s, what is the velocity of the car at the end of the breaking period? How far has the car moved during the breaking period? -10. m/s, 32 m

Sample #11 A baby sitter pushing a stroller starts from rest and accelerates at a rate of 0.500 m/s2. What is the velocity of the stroller after it has traveled 4.75 m? +2.18 m/s

Sample #12 Find the velocity after the stroller in #11 has traveled 6.32 m. +2.51 m/s

Sample #13 An aircraft has a liftoff speed of 120 km/h. What minimum constant acceleration does this require if the aircraft is to airborne after a take-off run of 240 m? +2.3 m/s2 How long does it take the aircraft to become airborne? 14 s

Let’s compare 5 cars!

Your goal is to establish a finish line that all 5 cars can cross simultaneously. They do not have to start at the same position. They should be powered by battery, rev motion or using a ramp set at a 45 degree angle. They do all need to cross your tape finish line at the same time. You should show all calculations prior to attempting experimental validation!