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3 years ago

Select the correct answer.

Physics

2 answers:

FinnZ [79.3K]3 years ago

8 0

2 hours is the answer because you do 45x2=90

Bumek [7]3 years ago

3 0

Answer:

B. 2 Hours

Explanation:

If you are going 45 miles per hour, you will travel 45 miles in 1 hour. It will take you 2 hours to travel 90 miles at a speed of 45 miles per hour.

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Alex, parked by the side of an east-west road, is watching car P, which is moving in a westerly direction. Barbara, driving east

Alexxandr [17]

Answer:

$v_{PB} = 130\ km/h$

Explanation:

Since, Alex is at rest. Therefore, the speed measured by him will be the absolute speed of car P. Therefore, taking easterly direction as positive:

$Absolute\ Velocity\ of\ Car\ P = v_{P} = -78\ km/h$

And the absolute velocity of Barbara's Car is given as: $Absolute\ Velocity\ of\ Barbara's\ Car = v_{B} = 52\ km/h$

Now, for the velocity of Car p with respect to the velocity of Barbara's Car can be given s follows:

$Velocity\ of\ Car\ P\ measured\ by\ Barbara = v_{PB} = v_{B}-v_{P}\\\\v_{PB} = 52\ km/h-(-78\ km/h)$

$v_{PB} = 130\ km/h$

6 0

3 years ago

A spaceship travels at 1,321 km/h. How many miles can it travel in 6.19 seconds?

sergiy2304 [10]

Answer:

2.271386111 km/s

Explanation:

1321÷60hrs÷60mins×6.19s=2.27km

7 0

3 years ago

Read 2 more answers

The drawing shows two long, thin wires that carry currents in the positive z direction. Both wires are parallel to the z axis. T

erica [24]

Answer:

The magnitude of the magnetic field at the origin is $2.56\times 10^{-6}\ T$ .

Explanation:

Given :

50-A wire is in the x-z plane and is 5 m from the z axis.

Also , 40-A wire is in the y-z plane and is 4 m from the z axis.

Now , since both the wire are perpendicular to each other .

Therefore , magnetic field are also perpendicular to each other .

Magnetic field at origin due to wire 1 is :

$B_1=\dfrac{\mu_oI_1}{2\pi R_1}\\\\B_1=\dfrac{(50)\mu_o}{2\pi( 5)}\\\\B_1=\dfrac{5\mu_o}{\pi}$

Magnetic field at origin due to wire 2 is :

$B_2=\dfrac{\mu_oI_2}{2\pi R_2}\\\\B_2=\dfrac{(40)\mu_o}{2\pi( 4)}\\\\B_2=\dfrac{4\mu_o}{\pi}$

Now , therefore net magnetic field is :

$B=\sqrt{B_1^2+B_2^2}\\\\B=\sqrt{(\dfrac{5\mu_o}{\pi})^2+(\dfrac{4\mu_o}{\pi})^2}\\\\B=\dfrac{\sqrt{41}\mu_o}{\pi}$

Putting value of $\mu_o=4\pi \times 10^{-7}\ H/m$

We get ,

$B=\sqrt{41}\times 4\times 10^{-7}\\B=2.56\times 10^{-6}\ T$

Therefore, the magnitude of the magnetic field at the origin is $2.56\times 10^{-6}\ T$ .

5 0

3 years ago

A conventional current of 8 A runs clockwise in a circular loop of wire in the plane, with center at the origin and with radius

alisha [4.7K]

Answer:

I2 = 3.076 A

Explanation:

In order to calculate the current in the second loop, you take into account that the magnitude of the magnetic field at the center of the ring is given by the following formula:

$B=\frac{\mu_oI}{2R}$ (1)

I: current in the wire

R: radius of the wire

μo: magnetic permeability of vacuum = 4π*10^-7 T/A

In the case of the two wires with opposite currents and different radius, but in the same plane, you have that the magnitude of the magnetic field at the center of the rings is:

$B_T=\frac{\mu_oI_1}{2R_1}-\frac{\mu_oI_2}{2R_2}$ (2)

I1: current of the first ring = 8A

R1: radius of the first ring = 0.078m

I2: current of the second ring = ?

R2: radius of the first second = 0.03m

To find the values of the current of the second ring, which makes the magnitude of the magnetic field equal to zero, you solve the equation (2) for I2:

$\frac{\mu_oI_2}{2R_2}=\frac{\mu_oI_1}{2R_1}\\\\I_2=I_1\frac{R_2}{R_1}=(8A)\frac{0.03m}{0.078m}=3.076A$

The current of the second ring is 3.076A and makes that the magntiude of the total magnetic field generated for both rings is equal to zero.

5 0

3 years ago

A tennis ball traveling horizontally at a speed of 40 m/s hits a wall and rebounds in the opposite direction. The time Interval

liubo4ka [24]

Answer

given,

initial velocity of the ball, u = 40 m/s

final velocity of the ball, v= -40 m/s

time of contact = 0.013 s

mass of the ball = 0.059 Kg

a) initial momentum

P₁ = m u = 0.059 x 40 = 2.36 kg.m/s

final momentum

P₂ = m v = 0.059 x (-40) = -2.36 kg.m/s

b) change in momentum

Δ P = P₂- P₁

Δ P = -2.36 - 2.36

Δ P = -4.72 kg.m/s

c) Average force

average force exerted by the ball is equal to change in momentum per unit time.

$F =\dfrac{\Delta P}{t}$

$F =\dfrac{-4.72}{0.013}$

F = -363 N

3 0

4 years ago