physics review - answers accelerated motion, free-fall, and the law of inertia

Physics Review - answers

Accelerated motion, free-fall, and Accelerated motion, free-fall, and the Law of Inertiathe Law of Inertia

What does the slope of a line on a position vs. time graph

mean?

velocity

What does the slope of a line on a velocity vs. time graph

mean?

acceleration

What does the area under the line on a velocity vs. time

graph mean?

displacement

In the first unit of time the bb falls 1 cm as shown.

What is the position of the bb after 3 units

of time?

9 cm

A ball is dropped from rest as shown in the figure. What is the

speedometer reading at 3 seconds?

30 m/s

Joe’s reaction time was 0.12 seconds. He is driving at 20 m/s and sees an obstacle in

the road. How far will he move before he can apply the

brakes?2.4 m

What happens to an unbuckled Kermie when his cart hits a wall?

He continues to move forward and hits the wall

An object is thrown straight upward with a velocity of +50 m/s. At what time will it reach

its highest point?

t = 5 s

An object is thrown straight upward with a velocity of +20 m/s. What is its velocity at its

highest point?

0

Carts were released from rest along two different inclines.

Which car was on the steeper incline?

Cart A

Cart Bposition

time

Cart A

Carts were released from rest along two different inclines.

Which cart was on the shallower incline?

velocity

time

Cart C

Cart D

Cart D

Describe the motion of this car

Time (s)

Position

(m)

y = 20x + 0

Moving at a constant velocity of 20 m/s

A ball is dropped from rest as shown in the

diagram. What is the speedometer

reading at 5 seconds?

50 m/s

Which color car is moving faster?

X(m)

Time (s)

red

What is happening at the point where the two lines cross?

X(m)

Time (s)

Same place at same time

Describe the motion of these two cars

X(m)

Time (s)

Blue – constant speed

Red - accelerating

Do these two cars ever have the same velocity?

v(m/s)

Time (s)

yes

A plane traveling toward the left wants to drop a package on the X.

At what point must the plane drop the package?

C

Describe the a-t graph that matches this motion

v(m/s)

Time (s)

0

Flat line above 0

Describe the a-t graph that matches this motion

v(m/s)

Time (s)

0

Flat line below 0

An object is thrown straight upward with a velocity of +50 m/s. What is its acceleration

at the highest point?

-10 m/s2

A marble and a bowling ball are dropped from a tower. Ignoring air resistance,

which strikes the ground first?

Both strike same time

Describe the motion of this object

t = 0

X = 0X = 1 m X = 4 m X = 9 m

acceleration

What is the displacement of this object for the first 3 s?

15 m

What is the average velocity for the first 3 s?

5 m/s

Determine the displacement for the first 3 s.

9 m

Determine the instantaneous velocity at t = 2 s.

2 m/s

What is the acceleration of this object?

- 2 m/s2

A rock is dropped from a bridge and it takes 3 seconds to hit the water. How high is the bridge above the water?

Ignore air resistance.

45 m

Describe the motion of this object

t = 0

X = 0X = 1 m X = 4 m X = 9 m

Constant speed

What is the object’s velocity at t = 7 s?

0

30

60

0 1 2 3 4 5 6 7 8 9 10

11

12

13

14

15

16

17

18

19

20

Time (sec)

Velocity (m/s)

30 m/s

What is the object’s acceleration at t = 18 s?

0

30

60

0 1 2 3 4 5 6 7 8 9 10

11

12

13

14

15

16

17

18

19

20

Time (sec)

Velocity (m/s)

12.5 m/s2

What is the object’s displacement between t = 5 and t = 9 s?

0

30

60

0 1 2 3 4 5 6 7 8 9 10

11

12

13

14

15

16

17

18

19

20

Time (sec)

Velocity (m/s)

120 m

Where is the object at t = 20 s?

0

30

60

0 1 2 3 4 5 6 7 8 9 10

11

12

13

14

15

16

17

18

19

20

Time (sec)

position (m)

10 m

An object is thrown straight upward with a velocity of +40 m/s. At what time will it reach

its highest point?

4 s

What is the difference between speed and

velocity?

Speed is how fast; velocity is speed and direction

Example of an accelerating object that

has constant speed

Object moving in a circular path

What is the velocity of an object 7 seconds after being thrown upward with an initial velocity of +50 m/s upward?

-20 m/s

Who was the person who first published a book that

suggested the Earth moves around the Sun?

Copernicus

What is the usual reason that an object sliding along a flat

surface stops?

friction

An object in motion will continue moving at a constant

speed in a straight line UNLESS ________

An unbalanced force acts

A ball is whirled around in a circle on a string. The string breaks when the ball is at the point shown below. Which letter best describes the

path of the ball after the string breaks?

b