Answer:
. Doppler ultrasound is based on absorption of sound, and other
ultrasound technology is based on reflection.D.
Explanation:
The force required to slow the truck was -5020 N
Explanation:
First of all, we find the acceleration of the truck, which is given by

where
v is the final velocity
u is the initial velocity
t is the time
For the truck in this problem,
v = 11.5 m/s
u = 21.9 m/s
t = 2.88 s
So the acceleration is

where the negative sign means that this is a deceleration.
Now we can find the force exerted on the truck, which is given by Newton's second law:

where
m = 1390 kg is the mass of the truck
is the acceleration
And substituting,

So the closest answer among the option is -5020 N.
Learn more about acceleration and forces:
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Answer:
a. an increase in the mass on the spring.
Explanation:
T = 2π/ω = 2π/√(k/m) = 2π√(m/k)
2π is a constant
as m is in the numerator, increasing mass will increase the period.