Unit 03“Horizontal

Motion”

Problem Solving

Problem Solving Steps

1st List Variables & Assign Values2nd Choose Equation3rd Plug In4th Solve (Simply and/or Rearrange)5th Box Answer

1.Edelin started to drive her car with an initial velocity of 10m/s. If she drives for 5 seconds with an acceleration of 4m/s2, what is her final velocity?

Vi =

Δt =a =Vf =

1st List Variables and Assign Values

Vf = Vi + aΔt2nd Choose Equation

3rd Plug In

4th Solve (Simply, Rearrange)

5th Box Answer

1.Edelin started to drive her car with an initial velocity of 10m/s. If she drives for 5 seconds with an acceleration of 4m/s2, what is her final velocity?

Vi =

Δt =a =Vf =

1st List Variables and Assign Values

Vf = Vi + aΔt2nd Choose Equation

3rd Plug In

4th Solve (Simply, Rearrange)

5th Box Answer

10m/s

5s

4m/s2

?

Vf = Vi + a Δt10m/s (4m/s2) (5s)

Vf = 10m/s+ (4m/s2)(5s)20m/sVf = 10m/s + 20m/s30m/s

Vf = 30m/s

2. How far does a car travel if, starting with a velocity of 5m/s, it drives for 10 seconds while accelerating at 3m/s2?

2. How far does a car travel if, starting with a velocity of 5m/s, it drives for 10 seconds while accelerating at 3m/s2?

Δx =Vi =

Δt =a =

?5m/s10s3m/s2

Δx = ViΔt + ½aΔt2

Δx = (5m/s)(10s) + ½(3m/s2)(10s)2

Δx = (5m/s)(10s) + ½(3m/s2)(100s2)

Δx = (50m) + ½(300m)

Δx = 50m + 150m

Δx = 200m

3. A rollercoaster starts from rest and accelerates at a rate of 4m/s2 for 200m. How long does it take to reach this point?

3. A rollercoaster starts from rest and accelerates at a rate of 4m/s2 for 200m. How long does it take to reach this point?

Δt = ?

Δx = 200m

Vi = 0 m/s

a = 3m/s2

Δx = ViΔt + ½aΔt2

200m = (0m/s)(Δt) + ½(4m/s2)(Δt)2

200m = (0) + (2m/s2)(Δt)2

200m = (2m/s2)(Δt)2

100s2 = (Δt)2

10s = Δt

2m/s22m/s2

√√

4. If the rollercoaster car is moving at a speed of 5m/s and then accelerates to a final speed of 8m/s over a distance of 450m, what is the car’s acceleration?

Vi =

Vf =

Δx =a =

Vf2 = Vi

2 + 2aΔx5m/s

450m

8m/s

?(8m/s)2 = (5m/s)2 + 2a(450m)

64m2/s2 = 25m2/s2 + 900m(a)

39m2/s2 = 900m(a)

0.0433m/s2 = a

-25m2/s2-25m2/s2

900m900m

Easy Practice ProblemsSolve the following EASY problems on your white board in your small groups.

1)Delyla kicks a soccer ball from rest giving it an acceleration of 1.5m/s2 for 14s, how fast does it go in the end?2)Issa slows his car from a velocity of 30m/s for 12s with an acceleration of -3m/s2, how far did he go?3)Joan is pushing his brother on his bike when he asks him to go faster. If the bike changes speed from 4m/s to 8m/s in 10seconds, how far have the brothers traveled in this time?4)What is the final velocity of a car driven by Mr. Hunt if it starts from rest and accelerates at a rate of 2m/s2 for 25m?

#1 Answer: 21m/s #2 Answer: 144m

#3 Answer: 60m

#4 Answer: 10m/s

Medium Practice ProblemsSolve the following Medium problems on your white board in your small groups.

5)Chanda bikes with a velocity of 12m/s and then accelerates at 3 m/s2 for 20m. What is her final velocity? 6)What is the acceleration of Michael’s car if he starts with a velocity of 40m/s and speeds up to a velocity of 70m/s for 3 seconds as he races around the Thurber’s Avenue curve on route 95?7)Destiny pushes a soccer ball so it accelerates from a velocity of 8m/s to 2m/s. If it rolls for 2 seconds, what is the acceleration?8)What is the initial velocity of a ball that Ms Bucci pushes to accelerate at 2m/s2 for 7 seconds and ends with a final velocity of 35m/s?9)Tylor rides his bicycle with a velocity of 12m/s, if he accelerates at a rate of 3m/s2 and ends with a velocity of 38m/s, how long did it take?

#5 Answer: 16.2m/s

#6 Answer: 10m/s2 #7 Answer: -2m/s2

#8 Answer: 21m/s

#9 Answer: 8.67s

6. What is the acceleration of Micahel’s car if she starts with a velocity of 40m/s and speeds up to a velocity of 70m/s for 3 seconds as she races around the Thurber’s Ave curve of route 95? Vf = Vi + a∆t

70m/s= 40m/s + (a)(3s)30m/s = (a)(3s)

10m/s2 = a

Vi = 40m/sVf = 70m/sΔt = 3sa = ?

Medium Example