Answer:
a) 915 m
b) 0.15 W/
Explanation:
solution:
a) The wavelength of the microwaves electromagnetic wave is:
λ=
=
=0.025 m
the circular radar antenna acts like a circular aperture of diameter D will have a bright central maximum of diameter:
w=2.44λL/D
so at 30 km screen:
w=2.44λL/w
=2.44*0.025*30*10^3/2
=915 m
b)
The area of a beam at 30 km is:
A=
=
=
=
the average microwave intensity is equal to the ratio of the power of the antenna and area of the beam:
I=P/A
So at 30 km:
I=100*10^3/657*10^3
=0.15 W/
This is more along the lines of "Does gravity affext potential energy"
Sort of. Potential energy is an odd one to imagine, sometimes.
It's the energy possessed by an object or system by dint of it's spatial
and mechanical configuration.
That definition alone is perhaps not so useful...and it's certainly not
official. But what it means is that an object can potentially have
energy due to where it is or what state the system is in.
Imagine we have a box and it's on the floor. The box, for all intents
and purposes, has no potential energy. It isn't going anywhere and it
just sits on the floor. It can't do any work in it's current position.
Now we hoist the box into the air. For any distance the box travels from
the floor, it gains potential energy. Now let's back track. We've
changed the box's spatial configuration by hoisting it into the air and
so have given it potential energy.
Why does it now have potential energy? Because we can now drop the box
(costing us no energy) and the box will fall. Maybe it falls onto a
passer-by and injures them.
Box on the floor = No energy.
We lift the box = We spend our energy and give the box potential energy
(as it wants to fall toward the ground).
We drop the box = Potential energy is converted to kinetic energy as the
box falls.
Box injures someone = The kinetic energy has done work upon the person.
So we can see how it all flows and connects. We have to put energy into
the box to fight against gravity, but you can't destroy or create
energy....so the energy we've spent is potentially stored 'inside' the
box.
Clearly, gravity effects a LOT of potential energies around us. In fact
to some small extent, it's probably impossible to entirely avoid it's
effects.
Answer:
Average speed = 2.5 mph
Distance = 22.352 meters
Explanation:
Calculate speed, distance or time using the formula d = st, distance equals speed times time.
Calculate speed, distance or time using the formula d = st, distance equals speed times time.
You can use this formula for any question like this
