Objective: MCAS review- Speed and Acceleration Homework: Finish questions

Do Now: Answer in notes:Answer in notes: Look up the equation for average acceleration and write it down.

A car has an oil drip. As the car moves, it drips oil at a regular rate, leaving a trail of spots on the road. Which of the following diagrams of the car’s trail of spots shows the car continuously slowing down?A car has an oil drip. As the car moves, it drips oil at a regular rate, leaving a trail of spots on the road. Which of the following diagrams of the car’s trail of spots shows the car continuously slowing down? A. B. C. D. A. B. C. D. Slowing down = speed (or velocity) What variable and equation for velocity? Velocity = vv =∆x/∆t So to slow down, would need less distance over time

How to cheat using the formula sheet 1.Find what the question is asking for (underline) 2.Look up what’s underlined and find variable for it 3.Find equation that is for that variable 4.Read equation like sentence (may need to look up what other variables man in the equation) 5.Answer or solve the problem (if problem, use 4 steps for problem solving) Ex: “What is work?” Ex: W = Work Ex: W = Fd Ex: Work is force multiplied by distance

How far did the car move during the first 15 s of the trip? A.20 m A.20 m B.25 m C.300 m C.300 m D.500 m How far? Asking for… Distance or displacement Distance = d, displacement = x No equation for distance What have we can work with? Know velocity (v) and time (t) Use equation: Average velocity = ∆x/∆t Use triangle to solve for ∆x x ∆v ∆t ∆x= ∆v∆t Get numbers from graph ∆x = 20 x 15 = 300m

The graph below illustrates the position and time for a dog that runs to catch a stick and then returns with it. The dog caught the stick after 2 s. What was the dog’s average speed as he returned with the stick? A.His average return speed was 0.7 m/s. A.His average return speed was 0.7 m/s. B.His average return speed was 0.9 m/s. B.His average return speed was 0.9 m/s. C.His average return speed was 2 m/s. C.His average return speed was 2 m/s. D.His average return speed was 4 m/s. Average speed = d/∆t Now need to put in what known to solve equation. Get what known from graph Need data only for return part of trip. Remember return means line goes down (goes closer to home) d = 7-0 = 7m t =10-2= 8s Average speed = d/∆t Average speed= 7/8 =.87 =.9m/s

Two soccer players, X and Y, are kicking a ball back and forth to each other, as shown below. A soccer player is kicking a soccer ball to another player. The table below shows the distance and direction the ball moves after each of four kicks. KickPlayerDistance and Direction 1X5 m right 2Y4 m left 3X6 m right 4Y5 m left What is the total displacement of the ball and the total distance traveled by the ball? A.The ball has a displacement of 2 m to the right and traveled a distance of 20 m. B.The ball has a displacement of 20 m to the right and traveled a distance of 2 m. C.The ball has a displacement of 9 m to the right and traveled a distance of 11 m. D.The ball has a displacement of 11 m to the right and traveled a distance of 9 m. Distance how far in any direction; displacement how far from where started! Distance= = 20m Displacement= = 2m

Try this on your own! Use the problem solving steps and the formula sheet. How long will it take a car to accelerate from 20 m/s to 26 m/s at a rate of 1.4 m/s2? A.2.2 s A.2.2 s B.2.7 s B.2.7 s C.4.3 s C.4.3 s D.4.6 s How long: time = t We have Vi and Vf and acceleration. What equation has those and t in it? Average Accelration = ∆V/∆t Need to solve for t, so have to rearrange equation a ∆v ∆t ∆t = ∆v/a ∆t = 26-20/1.4 ∆t = 6/1.4= 4.3s

The graph below relates velocity to time. The graph would most likely apply to which of the following events? A.A soccer ball that is at rest is suddenly kicked. A.A soccer ball that is at rest is suddenly kicked. B.A ball is thrown upward and returns to the ground. B.A ball is thrown upward and returns to the ground. C.A person who is running at a constant speed decides to run faster. C.A person who is running at a constant speed decides to run faster. D.A car traveling at a constant speed applies its brakes and comes to a stop. Flat line= constant velocity Line down= velocity decreases v = 0

Write in notes What is the between speed and velocity? What is the difference between speed and velocity?