free fall, model problems 15­16.notebook
October 19, 2015
Aim: What are characteristics of free fall?
Predictions: On your paper, write down your predictions for the following scenarios. Give a reason for each of your predictions:
­You drop a textbook and a piece of paper side by side. Which will hit the table first?
­You place the piece of paper under the book and drop them together. Which will hit the table first?
­You place the piece of paper on top of the book and drop them together. Which will hit the table first?
1
free fall, model problems 15­16.notebook
October 19, 2015
2
free fall, model problems 15­16.notebook
October 19, 2015
3
free fall, model problems 15­16.notebook
October 19, 2015
4
free fall, model problems 15­16.notebook
October 19, 2015
5
free fall, model problems 15­16.notebook
October 19, 2015
6
free fall, model problems 15­16.notebook
October 19, 2015
7
free fall, model problems 15­16.notebook
1.
October 19, 2015
A rock is dropped from the top of a bridge whose height is 98m. a.
How long does it take for the rock to hit the water below?
b.
What is the speed of the rock as it enters the water?
8
free fall, model problems 15­16.notebook
2.
October 19, 2015
A stone is thrown upward with an initial velocity of 6 m/s. a.
How high above the point of release will the stone rise?
b.
What will be the velocity of the stone when it returns to your hand?
c.
For how long will the stone remain in the air?
9
free fall, model problems 15­16.notebook
October 19, 2015
3. A volcano shoots out blobs of molten lava, called lava bombs, from ground level. A geologist observing the eruption uses a stopwatch to tome the flight of a particular lava bomb that is projected straight upward. If the time for it to rise and fall back to the ground is 4.75 s, what was its initial speed?
10
free fall, model problems 15­16.notebook
4.
October 19, 2015
A ball is thrown downwards from a window at a speed of 2.0 m/s. a. How fast will it be moving when it hits the sidewalk 2.5 m below?
b. How much time elapses before the ball hits the sidewalk?
c.
If the ball had been thrown upwards at the same speed instead of downwards, how fast would it be moving when it hits the sidewalk?
11
free fall, model problems 15­16.notebook
5.
October 19, 2015
A hot air balloon is rising straight upward with a constant speed of 6.5 m/s. When the basket of the balloon is 20 m above the ground a bag of sand is released.
a. How long is the sandbag in the air before it hits the ground?
b. What is the greatest height above the ground the sandbag rises to?
What is the velocity of the sandbag when it strikes the ground?
c.
12
free fall, model problems 15­16.notebook
October 19, 2015
6. The acceleration due to gravity on Planet Sundara is one fourth of the acceleration due to gravity on Planet Earth. If an object takes 3 s to fall a certain distance from rest on Earth, how much time would it take the object to fall the same distance on Planet Sundara?
13
free fall, model problems 15­16.notebook
October 19, 2015
7. Launch Failure
A 7500 kg rocket blasts off vertically from the launch pad with a constant upward acceleration of 2.25 m/s2 and feels no appreciable air resistance. When it has reached a height of 525 m, its engines suddenly fail so that the only force acting on it is now gravity.
a) What is the maximum height the rocket will reach above the launch pad?
b) How much time after engine failure will elapse before the rocket crashes on to the launch pad?
c) What is the total time the rocket spends in the air?
d) How fast will the rocket be moving when it crashes?
14
free fall, model problems 15­16.notebook
October 19, 2015
15