A rocket test projectile is launched skyward at 88 m/sec (198 mi/hr). How high does it go?

vo = ?vfinal = ?

a = ?

time to reach peak, t = ?height reached, x = ?

When does it peak? What has happened by that point?

v = 0 tsec

m

sec

m )8.9(88 2−+=

tsec

m

sec

m )8.9(88 2−=−

tsec

msecm

=−−

28.988

= 9 sec

So 2

2

1

00attvxx +=− )81)(8.9()9)(88( 2

21

2 secsecsec

m

sec

m −+

= 792m – 396.9m= 395 m (1/4 mile)

9.8 m/sec2

88 m/sec

A ball is thrown straight upward and caught when it returns to the height from which it was released.

1. At its peak position, the ball’sA. instantaneous velocity is maximum.B. instantaneous velocity is zero.C. instantaneous acceleration is zero.D. both B & C are true.

2. The time to fall back from its peak position is A. greater than B. equal to C. less than

the time it took to climb that high.

3. The speed it builds up to downward by the moment it is caught is A. greater than B. equal to C. less than

the speed it was thrown upward with.

For objects for which air friction is negligible,

time up = time downspeed down = speed up

Two spheres of identical mass areReleased when the mechanism aboveIs triggered. One sphere is launched Horizontally by a spring, the other is simultaneously dropped from rest.

A. The launched sphere will reach the ground first.B. Both spheres touch ground at the same time. C. The dropped sphere reaches the ground first.

Galileo’s critics argued that if the earth moved:

A stone is flung horizontally at 8 m/secfrom a point 1100 meters above the baseof a cliff.How far away from the cliff does it land?

?

?

/80.9

11002

=Δ=

−==

−=Δ

xt

smga

my or +1100m

+9.80m/s

Careful!!!Actually ay = 9.8m/s2

ax = ?0

0

/8

0

0

=

=

y

x

v

smv

VERTICALLY2

221 )80.9(01100 t

s

mm −+=− t = 15 sec

HORIZONTALLY

)15)(/8( ssmx =Δ Δx = 120 m

Its y-component of motionis like dropping from rest!

5

15

25

35

45

10

20

30

40

50

5 10 15 20 25 30 35

Weight Support (floor)

Adding all these supporting forces together

some pull left,some pull right,some pull forward,some pull back

all tend to pull UP!

(a tug-of-war balancing)

Styrofoam bridge

weighted at center

Pressure applied to rigid glass bar