10/22 HS Physics update and homework due 10/29

Hi folks,

This week we covered gravity in a bit more detail and spent some time exploring gravity in relation to our acceleration and velocity formulas we've been working on.  To do this, we went outside and everyone got a chance to throw a ball as far and as high as they could.  We then calculated the height, the vertical velocity and the horizontal velocity of the throw.

For homework this week:

Read pages 168 - 179 in the Conceptual Physics book.

Do Review Questions 1 - 14 on page 180.

Also, calculate the answers to the following questions using the formulas we used today.  Also, we are in Newtonia so don't worry about air resistance.  :) 

1.  Using the first dive on this video https://youtu.be/ttetLjQ4du8?t=81

a.  If the platform is 30 m high, how long does it take him to hit the water?

b.  How fast is he going when he hits the water?  (Use the time you found from the first question)

2. Use the first drop from this video https://youtu.be/-6h65t2MOfU?t=286

a.  If the dam is 165 m high, how long does it take the ball to hit the ground?

b. How fast is the ball falling when it hits the ground?

3.  Use the first hit on this video video https://youtu.be/rojPcO_LwvM?t=49  The ball is in the air for 7 seconds.

a.  How high is this ball hit?  (Remember to 1/2 your time.  It goes up for half the time and comes down for half)

b.  What was the vertical speed of the hit?

c.  If that ball flew 76 m (about 250 ft) what was the horizontal speed of the ball?

4. Use the first throw on this video https://youtu.be/n5ctPAqt_wk?t=14  Assume the ball was in the air for 3 seconds.

a. How high does this ball go?

b. How fast is the vertical speed?

c. How fast is the horizontal speed if the throw was 70 m (about 230 ft)

5.  Use the first punt on this video https://www.youtube.com/watch?v=OtP1eRKW9PI  The ball is in the air for 6 seconds.

a.  a. How high does this ball go?

b. How fast is the vertical speed?

c. How fast is the horizontal speed if the punt was 82 m (about 91 yards)

Answers:

1.

a.)  d = 1/2at^2  

 30 = 1/2 10 t^2

 30 = 5 t^2

 6 = t^2

 2.5s = t

b). v= at

v = 10 x 2.5

v = 25 m/s about 56 mph!!!

2. 

a) d = 1/2at^2  

165m = 1/2 10 t^2

165 = 5 t^2

33 = t^2

5.7 s = t

b) v = at

 v = 10 x 5.7

 v = 57 m/s about 128 mph!!!!!

 3. Remember to half the time for the calculations since half the time was going up and the other half down.

a.)  d = 1/2 at^2

   d = 1/2 10 x 3.5^2

   d = 5 x 12.3

   d = 61.5 m about 202 ft

b ) v = at

     v = 10 x 3.5

     v = 35 m/s  or 115 mph

c) v = d/t

   v = 76 / 6   Use the full 6 seconds here because it did take the ball 6 seconds to travel that 76 m.

   v = 12.7 m/s  about 28 mph

 

4.  Remember to half the time for the calculations since half the time was going up and the other half down.

a) d = 1/2 at^2

    d = 1/2 10 x 1.5^2

   d = 5 x 2.25

   d = 11.25 m about 37 ft

b) v = at

   v = 10 x 1.5

   v = 15 m/s about 33 mph

c) v = d/t

    v = 70/3   Use the full time here.

   v = 23.3 m/s about 52 mph !!

5. Remember to half the time for the calculations since half the time was going up and the other half down.

a. d = 1/2 gt^2    

d = 1/2 x 10 x 3^2   

d = 5 x 9

d = 45 m  about 144 ft

b. v = at

v = 10 x 3

v = 30 m/s  about 67 mph!

c. v = d/t

v = 82 / 6  Use the full time here.

v = 13. 7 m/s  about 31 mph