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Ira Lisetskai [31]

2 years ago

13

Suppose a police officer is 1/2 mile south of an intersection, driving north towards the intersection at 30 mph. at the same tim

e, another car is 1/2 mile east of the intersection, driving east (away from the intersection) at an unknown speed. the officer's radar gun indicates 15 mph when pointed at the other car (that is, the straight-line distance between the officer and the other car is increasing at a rate of 15 mph). what is the speed of the other car?

2 answers:

IgorLugansk [536]2 years ago

6 0

Answer:

$v = 51.2 mph$

Explanation:

Velocity of police car

$v_p = 30 mph$ towards North

velocity of the car with respect to police car

$v_{cp} = 15 mph$

Speed of the other car is given with respect to police car so let say the speed of other car is "v"

Now the component of this speed along the line joining two cars is

$v_1 = v cos45$

similarly speed of police car along the line joining two cars is given as

$v_2 = v sin45$

now we can find the relative speed

$v_{12} = v_1 - v_2$

$15 mph = vcos45 - 30cos45$

$v = 51.2 mph$

aleksandr82 [10.1K]2 years ago

3 0

In triangle ABC , using Pythagorean theorem

BC = sqrt(AB² + AC²)

r = sqrt(y² + x²) eq-1

taking derivative both side relative to "t"

dr/dt = (1/(2 sqrt(y² + x²) ) ) (2 y (dy/dt) + 2 x (dx/dt))

dr/dt = (1/(2 sqrt(0.5² + 0.5²) ) ) (2 (0.5) (dy/dt) + 2 (0.5) (dx/dt))

dr/dt = (1/(2 sqrt(0.5² + 0.5²) ) ) ( v₁ + v₂)

15= (1/(2 sqrt(0.5² + 0.5²) ) ) ( - 30 + v₂)

v₂ = 51.2 m/s

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Indigenous people sometimes cook in watertight baskets by placing hot rocks into water to bring it to a boil. What mass of 500ºC

scoray [572]

Answer:

m = 4.65 kg

Explanation:

As we know that the mass of the water that evaporated out is given as

$m = 0.0250 kg$

so the energy released in form of vapor is given as

$Q = mL$

$Q = (0.0250)(2.25 \times 10^6)$

$Q = 56511 J$

now the heat required by remaining water to bring it from 15 degree to 100 degree

$Q_2 = ms\Delta T$

$Q_2 = (4 - 0.025)(4186)(100 - 15)$

$Q_2 = 1.41\times 10^6J$

total heat required for above conversion

$Q = 56511 + 1.41 \times 10^6 = 1.47 \times 10^6 J$

now by heat energy balance

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4 0

2 years ago

An astronaut weighs 200 lb at sea level. The radius of the earth is 3960 miles. What force is exerted on the astronaut if he is

LiRa [457]

Answer:

85.31 N

Explanation:

Given,

Radius of Earth = 3960 miles = 6373 Km

Weight of Astronaut at Sea level = 200lb = 90.72 Kg

Altitude of Astronaut above Earth = 125 miles = 201.17 km

We know that,

$F = m\times g$ -------------------------- (1)

where,

F = force on the object due to gravity also called the weight

m = mass of the object = 200 lb = 90.71 kg

g = acceleration due to gravity = 9.8 m/s²

Also,

$F = \frac{GMm}{r^{2}}$ -------------------(2)

where,

F = force due to gravity

G = Gravitational constant = $6.67\times 10^{-11}$ Nm²/kg²

M = mass of the Earth = $5.97\times 10^{24} kg$

r = distance between the two objects

here, r = (6373+201.17)km = 6574170 m

From equation (1),

$m\times g = 90.71\\m=\frac{90.71}{g} \\m=\frac{90.71}{9.8}\\m=9.26 kg\\$

Putting value of m in equation (2)

$F = \frac{6.67\times 10^{-11}\times 5.97\times 10^{24}\times 9.26}{6574170^{2}}\\$

$F=85.31N$

6 0

2 years ago

two negative charge of -2.0 c and a positive charge of 3.0 c are separated by 80 m what is the force between two charges

kozerog [31]

The Coulomb force is equal to the constant k times the product of charge one and charge two over radius.

F=k((q1q2)/r)

6 0

2 years ago

The maximum tension that a 0.80 m string can tolerate is 15 N. A 0.35-kg ball attached to this string is being whirled in a vert

zimovet [89]

Answer:

v=5.86 m/s

Explanation:

Given that,

Length of the string, l = 0.8 m

Maximum tension tolerated by the string, F = 15 N

Mass of the ball, m = 0.35 kg

We need to find the maximum speed the ball can have at the top of the circle. The ball is moving under the action of the centripetal force. The length of the string will be the radius of the circular path. The centripetal force is given by the relation as follows :

$F=\dfrac{mv^2}{r}$

v is the maximum speed

$v=\sqrt{\dfrac{Fr}{m}} \\\\v=\sqrt{\dfrac{15\times 0.8}{0.35}} \\\\v=5.86\ m/s$

Hence, the maximum speed of the ball is 5.86 m/s.

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2 years ago

Two separate but nearby coils are mounted along the same axis. A power supply controls the flow of current in the first coil, an

gulaghasi [49]

Complete Question

The complete question is shown on the first uploaded image

Answer:

The correct answer is option c

Explanation:

Faraday states that when there is a change in magnetic field of a coil of a wire, it means that there exist an emf in the circuit which in induced due to the change in the magnetic flux

From the question two separate but nearby coils are mounted along the axis. First coil is connected to the power supply and the current flow is controlled by the supply.When the current alternates, it would produce magnetic field ,also the second coil is connected to an ammeter which indicates the current that is flowing in it when current in the first coil changes

This magnetic field that is produce would cause a change flux which would induce current in the second coil so the ammeter would indicate current flow in the second coil

a is incorrect because the current in fir coil is not change hence flux won't change therefore current is is not induced in second coil

This is the same reason b is incorrect

d is incorrect due to the fact that when the second coil is connected to a power supply by rewiring it to be in series with first coil the law of electromagnetism would no longer hold so he ammeter would show no reading

6 0

2 years ago