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3 years ago

14

A runner completes the 300-meter dash in 38 seconds. What is the speed of the runner? Round your answer the answer to the neares

t tenth.

1 answer:

loris [4]3 years ago

6 0

Answer:

speed = 7.9 m/s

Explanation:

speed = total distance / time taken

speed = 300 / 38

speed = 7.89473684 m/s

to the nearest tenth

speed = 7.9 m/s

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An object is launched from the top of a building which is 100 m tall (relative to the ground) at a speed of 22 m/s at an angle o

klio [65]

Answer:

$3.58\:\mathrm{s}$

Explanation:

We can use the kinematics equation $\Delta y=v_it+\frac{1}{2}at^2$ to solve this problem. To find the initial vertical velocity, find the vertical component of the object's initial velocity using basic trigonometry for right triangles:

$\sin28^{\circ}=\frac{y}{22},\\y=22\sin28^{\circ}=10.3283743813\:\mathrm{m/s}$

Now we can substitute values in our kinematics equation:

$\Delta y=-100$
$a=-9.8\:\mathrm{m/s^2}$ (acceleration due to gravity)
$v_i=-10.3283743813\:\mathrm{m/s}$
Solving for $t$

$-100=-10.3283743813t+\frac{1}{2}\cdot -9.8\cdot t^2,\\\\-4.9t^2-10.3283743813t+100=0,\\\\\boxed{t=3.5849312673637455}, t=-5.692762773751501\:\text{(Extraneous)}$

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3 years ago

A student pushes a laptop cart down the hallway by applying 20 Newtons force. The student pushes it 10 meters and

noname [10]

Answer:

None.

Explanation:

By definition, work is a process that it happens when an applied force

causes an object to change its position, i.e. to have a displacement.

Since the laptop cart is at rest while he stops at the water fountain, no

net work done is on the laptop cart.

4 0

3 years ago

The molecular mass of CO2.

mylen [45]

Answer:

the molrcular mass of carbon dioxide id 44.01amu

Explanation:

plz make me brainliest

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3 years ago

Read 2 more answers

A U-tube is open to the atmosphere at both ends. Water is poured into the tube until the water column on the vertical sides of t

zmey [24]

Answer:

The value is $\Delta h = 0.003 \ m$

Explanation:

From the question we are told that

The height of the water is $h_1 = 10 \ cm = 0.10 \ m$

The density of oil is $\rho_o = 950 \ kg/m^3$

The height of oil is $h_2 = 6 \ cm = 0.06 \ m$

Given that both arms of the tube are open then the pressure on both side is the same

So

$P_a = P_b$

=> Here

$P_a = P_z + \rho_w * g * h$

where $\rho_w$ is the density of water with value $\rho_w = 1000 \ kg/m^3$

and $P_z$ is the atmospheric pressure

and

$P_b = P_z + \rho_o * g * h_2$

=> $P_z + \rho_w * g * h = P_z + \rho_o * g * h_2$

=> $\rho_w * h = \rho_o * h_2$

=> $h = \frac{950 * 0.06 }{1000}$

=> $h = 0.057 \ m$

The difference in height is evaluated as

$\Delta h = 0.06 - 0.057$

$\Delta h = 0.003 \ m$

6 0

3 years ago

A person holding weights sits on a spinning stool. Then the person pulls the weights in,decreasing the rotational inertia of the

velikii [3]

Answer:

Ķ rot = 2K rot

When the arms and weight are retracted toward the body, the energy increases by twice the initial kinetic energy because the moment of inertia has decreased coupled with the energy needed to bring the hands towards the body.

Explanation:

K rot = kinetic energy of system when hands + weight are stretched out = ½ Iw²

Where w = angular velocity when arms and weight are stretched out

I = inertia of the system = ( Ie + Ip) where Ie= moment of inertia of the extra weight carried and Ip = moment of inertia of the person.

Ķ rot = final rotational energy when arms and external weight are pulled in = ½Ìŵ² where Ì =( Ìe + Ìp)

And Ìe = inertia of weight when hands are retracted and Ìp = inertia of person when hand are retracted

Using conservation of angular momentum which is

Iw = Ìŵ

Substitute ŵ = (I/Ì)*W in Ķ rot to give

Ķ rot =½Ì *[ (I/Ì) * W ]²

Ķ rot = ½ ( I²/Ì) * w²

Since K rot = ½ I w²

So Ķ rot = K rot ( I/Ì )...eq3

From the question above system inertia reduces by a factor of 2

Ì = ½I

Sub expression into equ3

Ķ rot = 2K rot

4 0

3 years ago