2RateA rate measures the change in one quantity in a particular length of time.(e.g.) 2 meters per second(e.g.) 5 revolutions per minute(e.g.) 30 belches per minute
3SpeedSpeed is the rate of change of position over a period of time.
4SpeedSpeed, velocity, and acceleration describe how an object’s position and motion change through time.
5SpeedAn object that moves at a constant speed travels the same distance each and every second.This hurdler is moving at a constant speedof 5 m/s (Every second, she goes 5 m):
6SpeedInstantaneous speed, or the speed of an object at a specific instant of time, is especially useful to measure for objects whose speed changes.A car driving in town must slow down and speed up, therefore its speed is not constant.
7SpeedAn object’s average speed is its total distance traveled divided by the total time it traveled.
8average speed = total distance The equation for average speed is:average speed = total distancetotal timeorv = dt
9Speed Use the triangle to solve word problems Cover up what’s missing & it tells you the math operation to use (multiply or divide)
10Speed1. Genna biked 20 km. in 2 hr. What is her speed?10 km/hr
11Speed2. Jason ran at 5 m/s for 30 s. How far did he run?150 m
12Speed 3. Geoff skated at 2 m/s for 200 m. How long did he skate for?
13SpeedIf you know any two quantities in the average speed equation, you can use the equation to calculate the third.
14SpeedThe unit for speed is a distance unit (meters) divided by a time unit (seconds). The SI unit for speed is m/s.
15VelocityVelocity is a measurement of both the speed and direction of motion of an object.
16VelocityVelocity is a vector. It has both a size (the speed of the object) and a direction (the direction the object is moving).The velocity vector of a ball changes when the direction and speed of the ball change.Where is its speed increasing?
17VelocitySpeed is different from velocity because speed does not include the direction in which the object is moving.
18AccelerationAcceleration, another vector, is the rate at which velocity changes over time.m/ss
19AccelerationWhen an object speeds up or slows down, its velocity changes, meaning that it is accelerating.
20AccelerationWhen an object speeds up, the direction of its acceleration is the same as the direction of its motion.
21AccelerationWhen an object slows down, its acceleration is in the opposite direction from the direction of its motion.
22AccelerationWhen an object changes the direction in which it is moving, its velocity changes. This means that it is accelerating.The horses on the carousel are constantly accelerating and changing direction, so they are constantly changing velocity even though their speed remains constant.
23Discuss:Is it possible to accelerate while standing still on the ground?
24Discuss:Is it possible to accelerate while standing still on the ground?Yes! It all depends on your point of reference. Even if you are standing still with respect to the ground beneath you, you are moving because Earth itself is moving. It rotates around its axis, and revolves around the Sun.
25Acceleration is the rate of change of ____. A velocity B speed C time 1.2 Speed, Velocity, and AccelerationAcceleration is the rate of change of ____.A velocityB speedC timeD direction
26A car stopping at a red light is an example of a(n) ____. 1.2 Speed, Velocity, and AccelerationA car stopping at a red light is an example of a(n) ____.A displacementB accelerationC directionD velocity
271.2 Speed, Velocity, and Acceleration It takes a runner 50 s to run a distance of 150 m. What is the runner’s average speed?A 0.3 m/sB 3 m/sC 100 m/sD 50 m/s
28A runner traveling at 5 m/s will cover what distance in 3 min? A 900 mB 90 mC 9 mD none of the above
29If a car travels 10 km in 5 min, stops for 2 min, and then travels 4 km in 3 min, what is the average speed of the car?A 14 km/hB 14 km/minC 1.4 km/minD 1.4 km/h
30Cars on an oval race track are accelerating because ____. A they are changing directionB their displacement is zeroC all of the aboveD none of the above
31If an object increases its speed, then it is ____. A changing velocityB changing directionC changing the reference directionD none of the above
32SCI 1.bWhich of the following is the rate of change in distance divided by time?A vectorB displacementC instantaneous speedD average speed
33SCI 1.cIf a car travels 45 km in half an hour, what is the average speed of the car?A 45 km/hB 45 km/minC 90 km/hD 90 m/s
34Velocity has both ____ and ____. A size; magnitude B size; speed SCI 1.dVelocity has both ____ and ____.A size; magnitudeB size; speedC speed; directionD direction; origin
35What occurs when an object accelerates? A It speeds up. SCI 1.eWhat occurs when an object accelerates?A It speeds up.B It slows down.C It changes direction.D all of the above