P201 Discussions Jan 15

Questions on Mastering Physics use?Using and interpreting motion

diagrams

1

Make up a story for each motion diagram

I

II

III

0 1 2 3 4

0 1 2 3 4 5 6

0123456

IV0 1 2 3 4 5

2

Q:1

120 s

Make up a story for each motion diagram

I0 1 2 3 4

III0 1 2 3 4 5 6

II0123456

IV0 1 2 3 4 5

Moving left, Stepping on the brakes

Moving right,“Steady as she goes”

Moving right,Stepping on the gas

Moving right,slower thenabruptly faster

3

Motion Diagrams

• Match the motion diagram with the situation.

(X) Mars explorer making a soft landing

(Y) Ball dropped from a rooftop

(Z) Dust particle settling at constant speed

Answer Choices:

(1) XA, YB, ZC

(2) XA, YC, ZB

(3) XB, YA, ZC

(4) XB, YC, ZA

(5) XC, YA, ZB

(6) XC, YB, ZC

Q:260 s

4

Motion Diagrams

• Match the motion diagram with the situation.

(X) Mars explorer making a soft landing

(Y) Ball dropped from a rooftop

(Z) Dust particle settling at constant speed

Answer Choices:

(1) XA, YB, ZC

(2) XA, YC, ZB

(3) XB, YA, ZC

(4) XB, YC, ZA

(5) XC, YA, ZB

(6) XC, YB, ZC

Q:2

5

Catching Up• Sue is sitting on the ground with her bike. Zoe rides by on her bike at a constant

velocity. About 20 seconds later Sue gets on her bike and accelerates until she catches Zoe about 40 seconds after that, and then rides along at the same speed. Which motion diagram best represents this?

20 s 40 s 60 s

20 s 60 s40 s

0 s

20 s 40 s 60 s

20 s 60 s40 s

0 s

0 s

20 s 40 s 60 s

20 s 60 s40 s

0 s

0 s

A

B

C

Q:3120 s

6

Catching Up• Sue is sitting on the ground with her bike. Zoe rides by on her bike at a constant

velocity. About 20 seconds later Sue gets on her bike and accelerates until she catches Zoe about 60 seconds later, and then rides along at the same speed. Which motion diagram best represents this?

20 s 40 s 60 s

20 s 60 s40 s

0 s

20 s 40 s 60 s

20 s 60 s40 s

0 s

0 s

20 s 40 s 60 s

20 s 60 s40 s

0 s

0 s

A

B

C

Q:3

7

Who was moving faster?

T=0 s T=1 s T=2 s T=3 s T=4 s

T=0 s T=2 s T=4 s

A

B

8

Q:4

Who was moving faster?

T=0 s T=1 s T=2 s T=3 s T=4 s

T=0 s T=2 s T=4 s

A

B

They have the same average velocity. The displacementsare twice as long in B, but they take twice as much timecompared to the displacements in A. They could be describing the same motion of the same object.

9

Q:4

During which interval was the velocity the same for A and B?

T=0 s T=1 s T=2 s T=3 s T=4 sA

T=0 s T=1 s T=2 s T=3 s T=4 sB

10

Q:5

During which interval was the velocity the same for A and B?

T=0 s T=1 s T=2 s T=3 s T=4 sA

T=0 s T=1 s T=2 s T=3 s T=4 sB

11

Draw this motion diagram

• A race car accelerates down a straightaway, slows down approaching a 90° curve, then accelerates straight again. The entire motion takes place over about 15 seconds at the Indy 500 (average speed over 100 meter/second).

12