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Vedmedyk [2.9K]
4 years ago
11

You throw a rock straight up from the edge of a cliff. It leaves your hand at time t = 0 moving at 13.0 m/s. Air resistance can

be neglected. Find both times at which the rock is 4.00 m above where it left your hand. Enter your answers in ascending order separated by a comma. Express your answer in seconds.

Physics
2 answers:
Zarrin [17]4 years ago
7 0

Answer:

0.36s, 2.3s

Explanation:

Let gravitational acceleration g = 9.81 m/s2. And let the throwing point as the ground 0 for the upward motion. The equation of motion for the rock leaving your hand can be written as the following:

s = v_0t + gt^2/2

where s = 4 m is the position at 4m above your hand. v_0 = 13 m/s is the initial speed of the rock when it leaves your hand. g = -9.81m/s2 is the deceleration because it's in the downward direction. And t it the time(s) it take to get to 4m, which we are looking for

4 = 13t - 9.81t^2/2

4.905 t^2 - 13t + 4 = 0

t= \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

t= \frac{13\pm \sqrt{(-13)^2 - 4*(4.905)*(4)}}{2*(4.905)}

t= \frac{13\pm9.51}{9.81}

t = 2.3 or t = 0.36

aivan3 [116]4 years ago
6 0

Explanation:

Below is an attachment containing the solution.

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Answer:

Both balls will hit the ground at the same time

Explanation:

The factor which leads to ball falling is the gravity acting on the ball;

The motions along the path of both balls are independent and both balls will obey the following illustration

Using the third equation of motion

s = ut + ½at²

Where s = distance covered by both balls.

u = initial velocity of both balls. Since both balls start from rest, u = 0m/s

a = acceleration; and it's equal to acceleration due to gravity.

a = g

By substituton

s = 0 * t + ½gt²

s = 0 + ½gt²

s = ½gt²

Make t the subject of formula

gt² = 2s

t² = 2s/g

t = ±√(2s/g)

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So,

t = √(2s/g)

It'll take both balls √(2s/g) time to hit the floor

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The frictional torque exerted on the platform by the axle as the platform rotates will be;

\rm T_f \theta =\frac{1}{2} I [\omega^2-\omega_0^2]

<h3>What is torque?</h3>

Torque is the force's twisting action about the axis of rotation. Torque is the term used to describe the instant of force. It is the rotational equivalent of force. Torque is a force that acts in a turn or twist.

The amount of torque is equal to force multiplied by the perpendicular distance between the point of application of force and the axis of rotation.

Work done by the frictional torque = Change in the rotational kinetic energy of the wheel

\rm T_f \theta =\frac{1}{2} I [\omega^2-\omega_0^2]

Where,

\rm T_f is the frictional torque

\rm \omega is the final angular velocity

\rm  \omega_0 is the initial angular velocity

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\rm T_f \theta =\frac{1}{2} I [\omega^2-\omega_0^2]

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brainly.com/question/6855614

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Which are examples of convection currents ? Select three options.
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<u>Answer</u>:

(B) A pot being heated by an electric burner

(D) A radiator that emits warm air and draws in cool air

(E) A hot air balloon rising and falling in the atmosphere​

These are some of the examples of the convection currents.

<u>Explanation</u>:

Earlier, electrons were believed to have positive charges and then electric current were discovered. But later after the invention of electric current and current which is termed to be the flow of electrons and is usually flows from negative to positive terminal. But its convention is not discarded in which current moves from positive terminal to negative and it is called convention current. The direction of current shown in the circuit is said to be the convention current.

Hence, the following are the examples of convention current.

1.  Boiling water - The energy travels into the pot from the burner, boiling down the water. Then this warm water is accumulating on the top and colder one is heading down to absorb it, triggering a circular motion.

2. Radiator - Place hot air at the peak and pull cool air at the bottom.

3. Hot air balloon - The air is warmed up by a heating element within the balloon, so the air jumps upwards. This induces the balloon to increase in size due to the inside trapping of the warm air. He removes a few of the warm air when the pilot commences to dive, and cold air takes place, enabling the parachute to drop.

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Answer:

Speed, v=1.86\times 10^8\ m/s

Explanation:

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E(x,t)=A\ cos[(1.57\times 10^7)x-(2.93\times 10^{15})t].....(1)

The general equation of wave is given by :

E=Acos(kx-\omega t)........(2)

On comparing equation (1) and (2)

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\dfrac{2\pi}{\lambda}=(1.57\times 10^7)

\lambda=\dfrac{2\pi}{(1.57\times 10^7)}

Wavelength, \lambda=4.002\times 10^{-7}\ m

\omega=(2.93\times 10^{15})

\dfrac{2\pi}{T}=(2.93\times 10^{15})

\dfrac{1}{T}=\dfrac{(2.93\times 10^{15})}{2\pi}

Frequency, f=4.66\times 10^{14}\ Hz

Let v is the speed of the light wave. It is given by :

v=f\times \lambda

v=4.66\times 10^{14}\ Hz\times 4.002\times 10^{-7}\ m

v=1.86\times 10^8\ m/s

So, the speed of the light wave is 1.86\times 10^8\ m/s. Hence, this is the required solution.

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4 years ago
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