When the projectile is at its maximum height above ground, it's at the point
of changing from rising to falling. At that exact point, its vertical speed is zero,
so the 14 m/s must be all horizontal velocity. That's not going to change.
Since we need to consider changes in vertical speed now, we need to make
some assumption about where this is all happening, so that we know the
acceleration of gravity. I'll assume that it's all happening on or near the Earth,
and the acceleration of gravity is 9.8 m/s².
I'm also going to neglect air resistance.
a). 1.2 sec before it reaches its maximum height, the projectile is rising
at a vertical speed of (1.2 x 9.8) = 11.76 m/s.
The magnitude of its velocity is
the square root of (14² + 11.76²) = 18.28 m/s, directed about 40° above horizontal.
b). 1.2 sec after it reaches its maximum height, the projectile is falling
at a vertical speed of (1.2 x 9.8) = 11.76 m/s.
The magnitude of its velocity is
the square root of (14² + 11.76²) = 18.28 m/s, directed about 40° below horizontal.
===========================
In 1.2 second before or after zero vertical speed, an object in free fall moves
(1/2) (g) (t²) = (4.9) (1.2²) = 7.06 meters .
c). & d).
1.2 seconds before it reaches maximum height, the projectile is located at
x = -14 m
y = -7.06 m
e). & f).
1.2 seconds after it reaches maximum height, the projectile is located at
x = +14 m
y = -7.06 m .
I hope you recognize that 6 answers, plus a little bit of explanation,
all for 5 points, ain't too shabby. You made out well.
Because there's no such thing as "really" moving.
ALL motion is always relative to something.
Here's an example:
You're sitting in a comfy cushy seat, reading a book and listening
to your .mp3 player, and you're getting drowsy. It's so warm and
comfortable, your eyes are getting so heavy, finally the book slips
out of your hand, falls into your lap, and you are fast asleep.
-- Relative to you, the book is not moving at all.
-- Relative to the seat, you are not moving at all.
-- Relative to the wall and the window, the seat is not moving at all.
-- But your seat is in a passenger airliner. Relative to people on the
ground, you are moving past them at almost 500 miles per hour !
-- Relative to the center of the Earth, the people on the ground are moving
in a circle at more than 700 miles per hour.
-- Relative to the center of the Sun, the Earth and everything on it are moving
in a circle at about 66,700 miles per hour !
How fast are they REALLY moving ?
There's no such thing.
It all depends on what reference you're using.
Answer:
2.3 Nm clockwise
Explanation:
Take counterclockwise to be positive and clockwise to be negative.
∑τ = (3 N) (2.5 m) − (7 N) (1.4 m)
∑τ = 7.5 Nm − 9.8 Nm
∑τ = -2.3 Nm
The net torque is 2.3 Nm clockwise.
Answer:
(i) Electric field outside the shell:
For point r>R; draw a spherical gaussian surface of radius r.
Using gauss law, ∮E.ds=q0qend
Since E is perpendicular to gaussian surface, angle betwee E is 0.
Also E being constant, can be taken out of integral.
So, E(4πr2)=q0q
So, E=4πε01r2q
