Motion ReviewDistance, Displacement, Scalar vs. Vector, Speed, Velocity,

Acceleration, Interpreting Graphs

A student leaves her science class and walks 10 meters north to a water fountain. Then she turns and walks 2 meters back to the library.

What distance does she travel?

a. 12m

b. 20m

c. 8m

d. 5m

A student leaves her science class and walks 10 meters north to a water fountain. Then she turns and walks 2 meters back to the library.

What is her displacement?

a. 12m north

b. 12m south

c. 8m north

d. 8m south

A softball player leaves the batter’s box and overruns 1st base by 3 m, then returns to the base. How does her displacement compare to her total distance run?

a. It is larger.

b. It is smaller.

c. It is the same.

Distance is a scalar, displacement is a vector quantity.

Displacement must always be a straight line and include the direction traveled from starting point to end point.

Remember…

A scalar quantity…

a. Always has mass.

b. Is fully described by its magnitude.

c. Shows direction

d. Does not have units.

 

Identify each of the following as Scalar or Vector. Distance Displacement Speed Velocity

Distance and speed are examples of scalar quantities.

Displacement and velocity are examples of vector quantities.

The SI unit for speed isa.mph.b.m/s.c.ft/s2.d.Dv / t.

On a velocity-time graph, a line with a negative slope indicates that the object isa.speeding up.b.not moving.c.slowing down.d.traveling at a constant speed.

An object that changes position relative to a reference point isa.stationary.b.moving at constant speed.c.in motion.d.moving at constant velocity.

Average speed can be represented by the mathematical expressiona. distance ÷ time.b. time – distance.c. distance × time.d. time + distance.

The _____ of an object consists of its speed and direction.

a.velocityb.average speedc.instantaneous speed d.displacement

The average speed of a runner who runs 500.0 m in 1.6 min is

a.0.19 m/s.b.96 m/s.c.5.2 m/s.d.312 m/s.

60 sec. = 1 min.

The average speed of a runner who runs 500.0 m in 1.6 min is

a.0.19 m/s.b.96 m/s.c.5.2 m/s.d.312 m/s.

60 sec. = 1 min.

A car moving at an average speed of 55.0 mi/h for 4.25 h has traveleda.0.08 mi.b.55 mi.c.13 mi.d.234 mi.

A car moving at an average speed of 55.0 mi/h for 4.25 h has traveleda.0.08 mi.b.55 mi.c.13 mi.d.234 mi.

On a distance vs. time graph of an object’s motion, distance is usually

a.plotted on the x-axis.b.the dependent variable.c.greater than time.d.measured in ft/min.

A pitcher throws a baseball to home plate, a distance of 60.5 ft. The ball reaches home plate in 0.63 s. What is the velocity of the ball?

a.38 ft/sb.96 ft/sc.38 ft/s toward home plated.96 ft/s toward home plate

A pitcher throws a baseball to home plate, a distance of 60.5 ft. The ball reaches home plate in 0.63 s. What is the velocity of the ball?

a.38 ft/sc.96 ft/sb.38 ft/s toward home plated.96 ft/s toward home plate

When the motion of an object is shown by a straight line on a distance vs. time graph with distance on the y-axis, the slope of the line is the

a.distance traveled.b.speed.c.displacement.d.time of travel.

Displacement must always indicate

a.velocity.b.speed.c.direction.d.time.

Speeding up, slowing down, and changing direction is best described as

a.velocity.b.displacement. c.distance.d.acceleration.

The equation for finding average acceleration for straight-line motion is

a.initial velocity – final velocity × time.b.final velocity – initial velocity/time.c.initial velocity + final velocity + time.d.initial velocity + final velocity – time.  

Moving from 0 m/s to 25 m/s in 8.0 s equals an average acceleration of

a.0.32 m/s.b.3.1 m/s.c.0.32 m/s2.d.3.1 m/s2.

Moving from 0 m/s to 25 m/s in 8.0 s equals an average acceleration of

a.0.32 m/s.b.3.1 m/s.c.0.32 m/s2.d.3.1 m/s2.

A cyclist is traveling from an initial speed of 10.0 m/s to a final speed of 14.5 m/s. What is her acceleration after 9.0 s?

a.0.5 m/s

b.45 m/s

c.0.5 m/s2

.45 m/s2

A cyclist is traveling from an initial speed of 10.0 m/s to a final speed of 14.5 m/s. What is her acceleration after 9.0 s?

a.0.5 m/s

b.45 m/s

c.0.5 m/s2

d.45 m/s2

Peter runs in a constant direction on a straight road. The velocity vs. time graph of Peter’s motion shows a straight line with a negative slope. What does the line tell you about Peter’s speed?a. It is increasing.b. It is decreasing, then increasing.c. It is decreasing.d. It is constant.

When velocity changes by the same amount over each time interval, acceleration is

a.zero.b.positive.c.constant.d.negative.

A cheetah can accelerate at up to 6.0 m/s2. How long does it take for a cheetah to speed up from 10.5 m/s to 12.2 m/s?

a.0.28 sb.3.5 sc.1.7 sd.10 s

A cheetah can accelerate at up to 6.0 m/s2. How long does it take for a cheetah to speed up from 10.5 m/s to 12.2 m/s?

a.0.28 sb.3.5 sc.1.7 sd.10 s

The distance traveled by an object divided by the time it takes to travel that distance is called

a.average velocity.b.average acceleration.c.average speed.d.negative acceleration.

On a distance vs. time graph, the line of an object at rest is a

a.curved line with a slope of zero.b.jagged line with a negative slope.c.flat line with a slope of zero.d.curved line with a positive slope.

The difference between speed and velocity is that velocity includes

a.direction.b.time.c.distance.d.weight.

In order to determine speed, you must know

a.only time.b.both time and distance.c.only distance.d.neither time nor distance.

When an object slows down, its acceleration is

a.positive. b.negative.c.centripetal.d.constant.

Displacement

a.must be in a particular direction.b.is the change in position of an object.c.must be a straight line.d.All of the above

On a speed vs. time graph, constant acceleration is represented by a

a.straight line.b.jagged line.c.slightly sloped line.d.steeply sloped line.

   Means “change of” and is found by taking final - initial.

Δ  Initial velocity/speed. Equals zero for an object that begins at

rest. Vi

  Units for velocity

m/s

Final velocity/speed. Equals zero for an object that is stopping. Vf 

   How far something moves in a certain amount of time; the slope

of a distance vs. time graph. Speed

 A variable that is not dependent on the other (on the x-axis). Independent variable

 The rate of change in the speed of an object (how fast something changes speed). Acceleration

 A measurement of how steep a line is. Slope

Speed or Velocity?

a)A person walking 2 mph north.velocity b) A bird flies 20 m/s.Speed

Are these are accelerating (yes or no)? a) At constant velocity? noB) Going 20 m/s around a corner? yesC) Stopping from 20 m/s. yesD) An object at rest.no

An object is accelerating at 10 m/s2. If the object starts at rest:

a) How fast is it going after 1 second? 10 m/sb) How fast will it be going after 3 seconds?30 m/s

An object is traveling 3 m/s.

a) How far does it travel each second?3 m B) How far will it go in 3 seconds?9m

Car A is going 12 m/s. Car B is going 20 m/s. a)Which car travels more distance each second? Bb)Which car reaches 50 m last? AWhich car goes 100 m?Both

Acceleration is the rate of change of velocity

Velocity is speed with direction.

Changing your direction means you are accelerating.

Acceleration

Positive VelocityZero Acceleration

Positive VelocityPositive Acceleration

Slope =

Be able to draw the vector.

For example:

Ray runs 30 feet north, 30 feet west, and then 30 feet south. What is his displacement in each direction? What is his total distance?

Explain why displacement and distance are not the same.

Displacement vs. Distance