cq_1_081

#$&*

Phy 121

Your 'cq_1_08.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.

** CQ_1_08.1_labelMessages **

A ball is tossed upward with an initial velocity of 25 meters / second. Assume that the acceleration of gravity is 10 m/s^2 downward.

• What will be the velocity of the ball after one second?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

a = -10m/s/s

`dt = 1s

Vf = 25m/s -10m/s/s *1s

Vf= 15m/s

#$&*

• What will be its velocity at the end of two seconds?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

a = -10m/s/s

`dt = 2s

Vf = 25m/s -10m/s/s *2s

Vf= 5m/s

@&

Good.

It's good to know how to use the equations, and to use the correctly, but you can also get these results from the meanings of the quantities, without using equations.

10 m/s^2 means a change of 10 m/s, every second, in the downward direction.

So starting with 25 m/s upward, after one second a change of 10 m/s downward leaves us with 15 m/s, and after another second the same change will leave us 5 m/s, still upward. After still another second the same change will bring us to 5 m/s downward, etc., etc..

*@

#$&*

• During the first two seconds, what therefore is its average velocity?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

vf = 5m/s

vAve= 25m/s + 5m/s / 2 = 15m/s

#$&*

• How far does it therefore rise in the first two seconds?

answer/question/discussion: ->->->->->->->->->->->-> :

15m/s * 2s = 30m = `ds

#$&*

• What will be its velocity at the end of a additional second, and at the end of one more additional second?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

a = -10m/s/s

`dt = 3s

Vf = 25m/s -10m/s/s *3s

Vf= -5m/s

v0 = 25m/s

a = -10m/s/s

`dt = 4s

Vf = 25m/s -10m/s/s *4s

Vf= -15m/s

#$&*

• At what instant does the ball reach its maximum height, and how high has it risen by that instant?

The ball reaches maximum height at vf = 0 and it has risen 31m.

0m/s = 25m/s + (-10m/s^2)`dt

-25m/s = (-10m/s^2)`dt

-25m/s/(-10m/s/s) = `dt = 2.5s

`ds = 25m/s / 2 * 2.5s

`ds = 12.5m/s * 2.5s

`ds = 31m

answer/question/discussion: ->->->->->->->->->->->-> :

#$&*

• What is its average velocity for the first four seconds, and how high is it at the end of the fourth second?

Vf = -15m/s

V0 = 25m/s

vAve = (25m/s - 15m/s) /2 = 5m/s

answer/question/discussion: ->->->->->->->->->->->-> :

#$&*

• How high will it be at the end of the sixth second?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

a = -10m/s/s

`dt = 6s

Vf = 25m/s -10m/s/s *6s

Vf = 25m/s - 60m/s = -35m/s

`ds = (25m/s - 35m/s) / 2 * 6s

`ds = -5m/s * 6s

`ds = 30m

#$&*

** **

15 minutes

** **

&#Good responses. See my notes and let me know if you have questions. &#

cq_1_081

#$&*

Phy 121

Your 'cq_1_08.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.

** CQ_1_08.1_labelMessages **

A ball is tossed upward with an initial velocity of 25 meters / second. Assume that the acceleration of gravity is 10 m/s^2 downward.

• What will be the velocity of the ball after one second?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

a = -10m/s/s

`dt = 1s

Vf = 25m/s -10m/s/s *1s

Vf= 15m/s

#$&*

• What will be its velocity at the end of two seconds?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

a = -10m/s/s

`dt = 2s

Vf = 25m/s -10m/s/s *2s

Vf= 5m/s

@&

Good.

It's good to know how to use the equations, and to use the correctly, but you can also get these results from the meanings of the quantities, without using equations.

10 m/s^2 means a change of 10 m/s, every second, in the downward direction.

So starting with 25 m/s upward, after one second a change of 10 m/s downward leaves us with 15 m/s, and after another second the same change will leave us 5 m/s, still upward. After still another second the same change will bring us to 5 m/s downward, etc., etc..

*@

#$&*

• During the first two seconds, what therefore is its average velocity?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

vf = 5m/s

vAve= 25m/s + 5m/s / 2 = 15m/s

#$&*

• How far does it therefore rise in the first two seconds?

answer/question/discussion: ->->->->->->->->->->->-> :

15m/s * 2s = 30m = `ds

#$&*

• What will be its velocity at the end of a additional second, and at the end of one more additional second?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

a = -10m/s/s

`dt = 3s

Vf = 25m/s -10m/s/s *3s

Vf= -5m/s

v0 = 25m/s

a = -10m/s/s

`dt = 4s

Vf = 25m/s -10m/s/s *4s

Vf= -15m/s

#$&*

• At what instant does the ball reach its maximum height, and how high has it risen by that instant?

The ball reaches maximum height at vf = 0 and it has risen 31m.

0m/s = 25m/s + (-10m/s^2)`dt

-25m/s = (-10m/s^2)`dt

-25m/s/(-10m/s/s) = `dt = 2.5s

`ds = 25m/s / 2 * 2.5s

`ds = 12.5m/s * 2.5s

`ds = 31m

answer/question/discussion: ->->->->->->->->->->->-> :

#$&*

• What is its average velocity for the first four seconds, and how high is it at the end of the fourth second?

Vf = -15m/s

V0 = 25m/s

vAve = (25m/s - 15m/s) /2 = 5m/s

answer/question/discussion: ->->->->->->->->->->->-> :

#$&*

• How high will it be at the end of the sixth second?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

a = -10m/s/s

`dt = 6s

Vf = 25m/s -10m/s/s *6s

Vf = 25m/s - 60m/s = -35m/s

`ds = (25m/s - 35m/s) / 2 * 6s

`ds = -5m/s * 6s

`ds = 30m

#$&*

** **

15 minutes

** **

&#Good responses. See my notes and let me know if you have questions. &#

cq_1_081

#$&*

Phy 121

Your 'cq_1_08.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.

** CQ_1_08.1_labelMessages **

A ball is tossed upward with an initial velocity of 25 meters / second. Assume that the acceleration of gravity is 10 m/s^2 downward.

• What will be the velocity of the ball after one second?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

a = -10m/s/s

`dt = 1s

Vf = 25m/s -10m/s/s *1s

Vf= 15m/s

#$&*

• What will be its velocity at the end of two seconds?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

a = -10m/s/s

`dt = 2s

Vf = 25m/s -10m/s/s *2s

Vf= 5m/s

@&

Good.

It's good to know how to use the equations, and to use the correctly, but you can also get these results from the meanings of the quantities, without using equations.

10 m/s^2 means a change of 10 m/s, every second, in the downward direction.

So starting with 25 m/s upward, after one second a change of 10 m/s downward leaves us with 15 m/s, and after another second the same change will leave us 5 m/s, still upward. After still another second the same change will bring us to 5 m/s downward, etc., etc..

*@

#$&*

• During the first two seconds, what therefore is its average velocity?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

vf = 5m/s

vAve= 25m/s + 5m/s / 2 = 15m/s

#$&*

• How far does it therefore rise in the first two seconds?

answer/question/discussion: ->->->->->->->->->->->-> :

15m/s * 2s = 30m = `ds

#$&*

• What will be its velocity at the end of a additional second, and at the end of one more additional second?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

a = -10m/s/s

`dt = 3s

Vf = 25m/s -10m/s/s *3s

Vf= -5m/s

v0 = 25m/s

a = -10m/s/s

`dt = 4s

Vf = 25m/s -10m/s/s *4s

Vf= -15m/s

#$&*

• At what instant does the ball reach its maximum height, and how high has it risen by that instant?

The ball reaches maximum height at vf = 0 and it has risen 31m.

0m/s = 25m/s + (-10m/s^2)`dt

-25m/s = (-10m/s^2)`dt

-25m/s/(-10m/s/s) = `dt = 2.5s

`ds = 25m/s / 2 * 2.5s

`ds = 12.5m/s * 2.5s

`ds = 31m

answer/question/discussion: ->->->->->->->->->->->-> :

#$&*

• What is its average velocity for the first four seconds, and how high is it at the end of the fourth second?

Vf = -15m/s

V0 = 25m/s

vAve = (25m/s - 15m/s) /2 = 5m/s

answer/question/discussion: ->->->->->->->->->->->-> :

#$&*

• How high will it be at the end of the sixth second?

answer/question/discussion: ->->->->->->->->->->->-> :

v0 = 25m/s

a = -10m/s/s

`dt = 6s

Vf = 25m/s -10m/s/s *6s

Vf = 25m/s - 60m/s = -35m/s

`ds = (25m/s - 35m/s) / 2 * 6s

`ds = -5m/s * 6s

`ds = 30m

#$&*

** **

15 minutes

** **

&#Good responses. See my notes and let me know if you have questions. &#