Answer:
Momentum is given by
p
=
m
v
. Impulse is the change of momentum,
I
=
Δ
p
and is also equal to force times time:
I
=
F
t
. Rearranging,
F
=
I
t
=
Δ
p
t
=
0
−
20
,
000
5
=
−
4000
N
.
Explanation:
Momentum before the collision is
p
=
m
v
=
2000
⋅
10
=
20
,
000
k
g
m
s
−
1
.
Assuming the truck comes to a complete halt, the momentum after the collision is
0
k
g
m
s
−
1
.
The change in momentum,
Δ
p
, is initial minus final
→
0
−
20
,
000
=
−
20
,
000
This is called the impulse:
I
=
Δ
p
. Impulse is also equal (check the units) to force times time:
I
=
F
t
.
We can rearrange this expression to make
F
the subject:
F
=
I
t
=
Δ
p
t
=
−
20
,
000
5
=
−
4000
N
The negative sign just means the force acting is in the opposite direction to the initial momentum.
(This will be the average force acting during the collision: collisions are chaotic so the force is unlikely to be constant.)
The unit measurement for sound can be expressed in terms of intensity and in decibels. The intensity of sound is the measure of its power over unit area. The common unit of measurement is in decibels. This is commonly used in measuring the extent of noise. The conversion from intensity to the decibel unit is through logarithmic function. The formula is:
dB = 10 log(I/I0), where I0 is 10^-12 Watts per square meter
Substituting the values to the equation,
84 = 10log(I/10^-12)
I = 0.0002512 W/m2
In scientific notation the intensity is 2.512 x 10^-4 W/m^2.
Rachel Carson was the author of the acclaimed environmental book, Silent Spring. The book was published in 1962.
It documented the negative effect that synthetic pesticides have on the environment, specifically on birds.
This book laid bare to the American public what chemical companies indirectly contributed to the environment.
The public furor this book caused led to the reversal of the national pesticide policy, a nationwide ban on DDT for agricultural uses, and inspired the creation of the U.S. Environmental Protection Agency.
Part a.
u = 0, the initial velocity
v = 60 mi/h, the final velocity
a = 2.35 m/s², the acceleration.
Note that
1 m = 1609.34 m.
Therefore
v = (60 mi/h)*(1609.34 m/mi)*(1/3600 h/s) = 26.822 m/s
Use the formula
v = u + at
(26.822 m/s) = (2.35 m/s²)*(t s)
t = 26.822/2.35 = 11.4 s
Answer: 11.4 s
Part b.
We already determined that v = 60 mi/h = 26.822 m/s.
t = 0.6 s
Therefore
(26.822 m/s) = (a m/s²)*(0.6 s)
a = 26.822/0.6 = 44.7 m/s²
Answer: 44.7 m/s²
The short answer (and the long one for that matter) is physical properties of chemicals. If you are being marked by a machine, likely the answer is going to be physical properties.