“Think First” MCs - Kinematics

• Partner up

• Whiteboards ready

• Write legibly and BIG-ly

• Take pictures to help you remember later

A stoplight (which is considered to be at the origin) 20 m to A stoplight (which is considered to be at the origin) 20 m to the west turns yellow. Your car is traveling west at 12 m/s. the west turns yellow. Your car is traveling west at 12 m/s. You hit the brakes and decelerate at a rate of 6.0 m/sYou hit the brakes and decelerate at a rate of 6.0 m/s22. Your . Your car stops before it reaches the stoplight.car stops before it reaches the stoplight.

A student in a physics class made a picture of this.A student in a physics class made a picture of this.

to = 0 sxo = + 20 mvo = – 12 m/sa = – 6.0 m/s2

Which of the following is labeled wrong?Which of the following is labeled wrong?1 xo

2 vo

3 a4 a & vo

5 all of the values are correct

x

A student in a physics class made a picture of the situation A student in a physics class made a picture of the situation but did not include the signs of the variables.but did not include the signs of the variables.

to = 0 sxo = __ 20 mvo = __ 12 m/sa = __ 6.0 m/s2

What are the signs of the three missing variables?What are the signs of the three missing variables?xo vo a

1 + – –2 + – +3 + + –4 + + +5 – – +

x

A stoplight (which is considered to be the origin) 20 m to the A stoplight (which is considered to be the origin) 20 m to the west turns yellow. Your car is traveling west at 12 m/s. You west turns yellow. Your car is traveling west at 12 m/s. You hit the brakes and decelerate at a rate of 6.0 m/shit the brakes and decelerate at a rate of 6.0 m/s22. Your car . Your car stops before it reaches the stoplight.stops before it reaches the stoplight.

The motion of a car is represented with the motion diagram The motion of a car is represented with the motion diagram below. The stoplight is at the origin.below. The stoplight is at the origin.

Which graph best matches the motion diagram?Which graph best matches the motion diagram?

5 No graph represents the motion correctly

v

t

1 v

t

2v

t3

v

t

4

x

vinitialvfinal

a

Which graph is the best representation of the car’s Which graph is the best representation of the car’s motion?motion?

x

t

1 x

t

2

5 No graph represents the motion correctly

x

t

3

t

x4

A stoplight 20 m to the west turns yellow. Your car is A stoplight 20 m to the west turns yellow. Your car is traveling west at 12 m/s. You hit the brakes and decelerate at traveling west at 12 m/s. You hit the brakes and decelerate at a rate of 6.0 m/sa rate of 6.0 m/s22. Your car stops before it reaches the . Your car stops before it reaches the stoplight (which is considered to be at the origin).stoplight (which is considered to be at the origin).

vo a 1 + –2 + +3 – +4 – –

A bicycle is moving on the road. Its motion is described by A bicycle is moving on the road. Its motion is described by the graph below. the graph below.

Below is a mathematical description of the same motion. Below is a mathematical description of the same motion. What should the signs of What should the signs of vvoo and and aa be to be consistent with be to be consistent with

the above graphical description?the above graphical description?

v

t

v = vv = voo + a t + a t

A hot air balloon is stationary in the sky as seen in the picture.

A person throws a ball up in the air at 5 m/s.

Which set of equations best matches this process?

1. Vf = (5.0 m/s) + (10 m/s2) t

2. Vf = ( - 5.0 m/s) + (10 m/s2) t

3. Vf = (5.0 m/s) + ( - 10 m/s2) t

4. Vf = ( - 5.0 m/s) + ( - 10 m/s2) t

5. Either 2 or 3 are correct

Which graph best represents this situation?Which graph best represents this situation?

x

t

1 5 Graphs 3 & 4

6 Graphs 2, 3 & 4

7 No graph represents the motion correctly

x

t

3

t

x4

The mathematical representation seen below is in a physics textbook.

2

2

1attvdd oo ++=

)constant(0

0

0

<>>

avd

o

o

x

t

2

Which description best represents this situation?Which description best represents this situation?

1 This is a car that is moving to the right and is accelerating in the same direction.

2 A ball was thrown upwards in the air at a speed of 20 m/s.

3 A ball was thrown downwards at a height of 5 m at a speed of 20 m/s.

Susy sees the mathematical representation below in her physics book.

advv

attvdd

o

oo

2

2

1

22

2

+=

++=

2/10

/20

5

sma

smv

md

o

o

−=

==

1. Yes, all three diagrams are consistent.

2. No, Diagram A is not consistent with the other two.

3. No, Diagram B is not consistent with the other two.

4. No, Diagram C is not consistent with the other two.

5. None of the diagrams are consistent.

Are these three diagrams consistent with each other?Are these three diagrams consistent with each other?

Alan sees the following three diagrams next to each other in his physics book.

x

t

v

t

a

tA CB

A car is moving along the road as seen in the motion diagram below.

Which set of equations best matches this process?

1. Vf = (5.0 m/s) + (10 m/s2) t

2. Vf = ( - 5.0 m/s) + (10 m/s2) t

3. Vf = (5.0 m/s) + ( - 10 m/s2) t

4. Vf = ( - 5.0 m/s) + ( - 10 m/s2) t

5. Either 2 or 3 are correct

x+

vfinalvinitial