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4 years ago

10

A rock is thrown from a bridge at an angle 30∘ below horizontal.immediately after the rock is released, is the magnitude of its

acceleration greater than, less than, or equal to g?

1 answer:

Wittaler [7]4 years ago

4 0

<span>The magnitude of the rock is equal to g. After the rock is released, there are no more forces acting on it, yet gravity remains. The initial inputs, on a bridge, at an angle of 30 deg below horizontal do not matter after the release.</span>

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A car travels at a constant velocity of 70 mph for one hour. At the second hour, the car’s velocity was 60 mph. At the third hou

katovenus [111]

When the velocity increases, then the acceleration will be positive and when the velocity decrease then the acceleration will be negative.

During the first hour, the velocity was 70 mph and during the seconds hour the velocity was 60 mph. Hence, the velocity decrease in the seconds hour. So, the acceleration will be negative during the second hour.

Now, during the third hour the velocity increases as it is 80 mph. Hence, the acceleration will be positive during the third hour.

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4 years ago

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4vir4ik [10]

Explanation:

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4 years ago

A worker kicks a flat object lying on a roof. The object slides up the incline 10.0 m to the apex of the roof, and flies off the

11111nata11111 [884]

Answer:15.20 m

Explanation:

Given

initial velocity $(v_i)=15 m/s$

inclined length=10 m

$\mu _k=0.435$

inclination $\theta =43.5^{\circ}$

$F_{net}=f_r+mg\sin \theta$

$a_{net}=\mu _kg\cos \theta +g\sin \theta$

$a_{net}=0.435\times 9.8\times \cos 43.5+9.8\times \sin 43.5$

$a_{net}=3.09+6.74=9.83 m/s^2$

$v^2-u^2=2as$

$v^2=15^2-2\times (9.83)10$

$v=5.31 m/s$

So Particle launches with a speed of 5.31 m/s at an angle of \theta $=43.5$

$h_{max}=\frac{u^2\sin^2\theta }{2g}$

$h_{max}=\frac{(5.31)^2\sin ^2(43.5)}{2\times 9.81}$

$h_{max}=0.679$

Total height raised is $0.679+\frac{10}{\sin 43.5} =15.20 m$

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3 years ago

Some Physics questions! Please help!

lesantik [10]

1) 260 km/h

Let's use the following convention:

positive x-direction = east

positive y-direction = north

Here we have to find the north component of the velocity's airplane, which means we have to find its y-component.

We can use the formula:

$v_y = v sin \theta$

where

v = 750 km/h is the magnitude of the plane's velocity

$\theta=20.0^{\circ}$ is the angle between the direction of the plane and the positive x-axis

Substituting,

$v_y = (750)(sin 20)=256.5 km/h \sim 260 km/h$

2) $24^{\circ}$ north of east

In order to find the direction of flight, we have to consider that the vector representing the displacement of the plane is the hypothenuse of a right triangle, of which the displacements along the east and north direction are the sides.

Therefore, we have

$v_x = 220 km$ is the displacement towards east

$v_y = 100 km$ is the displacement towards north

Therefore, the angle that gives the direction is given by

$tan \theta = \frac{v_y}{v_x}$

And substituting,

$\theta =tan^{-1}( \frac{100}{200})=24^{\circ}$

and this angle is measured north of east.

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4 years ago

We have all complained that there aren't enough hours in a day. In an attempt to fix that, suppose all the people in the world l

Natali5045456 [20]

Answer:

the duration of a day increases 4.96x10^-11 s

Explanation:

According the exercise:

R=radius of Earth=6.37x10^6 m

mE=mass of Earth=5.97x10^24 kg

m=average mass of people=55 kg

n=number of population=7x10^9

M=total mass=n*m=7x10^9*55=3.85x10^11 kg

v=speed=2.5 m/s

The moment of inertia of population is:

I=(2/3)*M*R^2=(2/3)*3.85x10^11*(6.37x10^6)=1.04x10^25 kg*m^2

The time taken per revolution is:

T=2πR/v=(2π*6.37x10^6)/2.5=1.6x10^7 rev/s

The angular speed is:

w=2π/T=2π/1.6x10^7=3.9x10^-7 rad/s

The angular momentum of population is equal to:

L1=I*w=1.04x10^25*3.9x10^-7=4.08x10^18 kg*m^2/s

The angular momentum of Earth is equal to:

L2=I*w=((2/5)*me*R^2)*(2π/24)=((2/5)*5.97x10^24*(6.37x10^6)^2)*(2π/(24*60*60))=7.1x10^33 kg*m^2/s

The change in length of the day is equal to:

T´=T*(L1/L2)=(24*60*60)*(4.08x10^18/7.1x10^33)=4.96x10^-11 s

8 0

3 years ago