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SAT Physics 3
Question 1:
Five particles charged with the same charge
+q
move with the same speed
v
in a magnetic field
B
, as shown above. Which particle experiences the highest magnetic force?
A
B
C
D
E
Question 2:
Two wires of circular cross-sectional areas have resistances R
_{1}
and R
_{2}
.
If ρ
_{1}
= 2ρ
_{2}
, l
_{1}
= 2l
_{2}
and r
_{1}
= 2r
_{2}
, what is the ratio R
_{1}
/R
_{2}
?
ρ
_{1}
, ρ
_{2}
are the resistivities of the two wires,
l
_{1}
, l
_{2}
are the lengths of the two wires,
r
_{1}
, r
_{2}
are the radii of the two wires.
1
1/2
1/4
2
4
Question 3:
Two wires carry identical currents
I
, as shown above. At which point is the magnetic field the strongest?
A
B
C
D
E
Question 4:
Two metallic bars slide along metallic rails at speeds v
_{1}
= .1m/s and v
_{2}
= .2m/s as shown above. The bar and the rails are situated in a magnetic field of 4T. What is the induced voltage in the bar and rails?
20mV
30mV
40mV
120mV
150mV
Question 5:
A police car with its siren on travels at a speed v
_{1}
toward a person. The frequency of the siren is f
_{1}
and the person hears the sound at a frequency f
_{2}
. If v
_{s}
is the speed of sound, v
_{1}
=
v
_{s}
f
_{2}
/f
_{1}
v
_{s}
(1 - f
_{2}
/f
_{1}
)
v
_{s}
(f
_{1}
/f
_{2}
- 1)
v
_{s}
(1 - f
_{1}
/f
_{2}
)
v
_{s}
(f
_{2}
/f
_{1}
- 1)
Question 6:
Violet light has a wavelength of 400nm. What is its frequency, if the speed of light is 3·10
^{8}
m/s?
5·10
^{14}
7.5·10
^{14}
10
^{15}
2·10
^{15}
5·10
^{15}
Question 7:
The activity of a radioactive sample at time t = 0s is A
_{0}
and the activity of the same radioactive sample at time t
_{1}
is A
_{1}
. What is the decay constant of the sample?
[ln(A
_{1}
/A
_{0}
)]/t
_{1}
[ln(A
_{0}
/A
_{1}
)]/t
_{1}
[ln(A
_{1}
- A
_{2}
)]/t
_{1}
[ln(A
_{1}
/A
_{0}
)]t
_{1}
e
^{(A1/A0)t1}