Answer: If the woodpecker drums upon a tree 5 times in one second, then the frequency is 5 Hz; each drum must endure for one-fifth a second, so the period is 0.2 s.
Momentum = (mass) x (speed)
Change in momentum = (force) x (time)
The initial momentum is (mass) x (speed) = 2500x 25 = 62,500 kg-m/s.
Since you want to <u>stop</u> the vehicle, that number is also the required <em>change</em>
in momentum ... you want the vehicle to wind up with zero momentum.
62,500 = (force) x (time) = 20 x force
Divide each side by 20 :
force = 62,500 / 20 = <em>3,125 newtons </em>
The change in kinetic energy of the car is equivalent to the change in its potential energy. Thus:
K.E = P.E
1/2 x mΔv² = mgΔh
h = (8.2² - 5²) / 2(9.81)
h = 2.15 meters
Accelerating means it is gaining speed
The only one that is gaining speed here is C
a flower pot falling from a second story window
The strength of the electromagnet depends directly on the
current (amps) in the wire that the coil is made out of.
That current is going to be determined by the voltage of the
battery or power supply that powers the magnet, and by the
resistance of the wire. So yes, the properties of the wire do
have a direct effect on the strength of the magnet. If you
tried to make an electromagnet with a coil of wet spaghetti,
it would work, but you would need a humongous power supply
to get any significant strength out of the magnet.
