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3 years ago

A medicine ball has a mass of 5 kg and is thrown with a speed of 2 m/s. what is its kinetic energy?

1 answer:

7 0

The kinetic energy of the ball is given by:
$K= \frac{1}{2}mv^2$
where m=5 kg is the mass of the ball and v=2 m/s is its speed. Substituting these numbers, we find the kinetic energy:
$K= \frac{1}{2} (5kg)(2m/s)^2=10 J$

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A 62-kg man standing on a scale in an elevator notes that as the elevator rises, the scale reads 821 N. What is the acceleration

FromTheMoon [43]

Answer:

Acceleration of the elevator = 13.242 m/s2.

Explanation:

Force is defined as the push or pull on an object with mass in kg that causes a change velocity. Force as a vector means it has both magnitude and direction.

Mathematically,

F = M*a

Where

F = force in Newton.

M = mass of the object in kg.

a = acceleration due to gravity in 9.81 m/s2.

Acceleration of the elevator = 821/62

= 13.242 m/s2.

5 0

3 years ago

Read 2 more answers

You are a member of a geological team in Central Africa. Your team comes upon a wide river that is flowing east. You must determ

Dovator [93]

Answer:

(a). The width of the river is 90.5 m.

The current speed of the river is 3.96 m.

(b). The shortest time is 15.0 sec and we would end 59.4 m east of our starting point.

Explanation:

Given that,

Constant speed = 6.00 m/s

Time = 20.1 sec

Speed = 9.00 m/s

Time = 11.2 sec

We need to write a equation for to travel due north across the river,

Using equation for north

$v^2-c^2=\dfrac{w^2}{t^2}$

Put the value in the equation

$6.00^2-c^2=\dfrac{w^2}{(20.1)^2}$

$36-c^2=\dfrac{w^2}{404.01}$ ....(I)

We need to write a equation for to travel due south across the river,

Using equation for south

$v^2-c^2=\dfrac{w^2}{t^2}$

Put the value in the equation

$9.00^2-c^2=\dfrac{w^2}{(11.2)^2}$

$81-c^2=\dfrac{w^2}{125.44}$ ....(II)

(a). We need to calculate the wide of the river

Using equation (I) and (II)

$45=\dfrac{w^2}{125.44}-\dfrac{w^2}{404.01}$

$45=w^2(0.00549)$

$w^2=\dfrac{45}{0.00549}$

$w=\sqrt{\dfrac{45}{0.00549}}$

$w=90.5$

We need to calculate the current speed

Using equation (I)

$36-c^2=\dfrac{(90.5)^2}{(20.1)^2}$

$36-c^2=20.27$

$c^2=20.27-36$

$c=\sqrt{15.73}$

$c=3.96\ m/s$

(b). We need to calculate the shortest time

Using formula of time

$t=\dfrac{d}{v}$

$t=\dfrac{90.5}{6}$

$t=15.0\ sec$

We need to calculate the distance

Using formula of distance

$d=vt$

$d=3.96\times15.0$

$d=59.4\ m$

Hence, (a). The width of the river is 90.5 m.

The current speed of the river is 3.96 m.

(b). The shortest time is 15.0 sec and we would end 59.4 m east of our starting point.

3 0

3 years ago

An object is at rest on the ground. The object experiences a downward gravitational force from Earth. Which of the following pre

Montano1993 [528]

Answer:

A) and B) are correct.

Explanation:

If the object is at rest, it means that no net force is exerted on it.

As the object experiences a downward gravitational force from Earth, in order to be at rest, it must experience an upward force with the same magnitude as the gravitational force on the object.

This force is supplied by the normal force, which can adopt any value in order to meet the condition imposed by Newton´s 2nd Law, and is always perpendicular to the surface on which the object is placed (in this case, the ground).

At a molecular level, this normal force is supplied by the bonded molecules of the ground that behave like small springs being compressed by the molecules of the object, exerting an upward restoring force upward on them.

So, the statements A) and B) are true.

6 0

2 years ago

Read 2 more answers

Nerve signals in the body occur when a small voltage, called an action potential, is applied across the membrane of a cell. When

nasty-shy [4]

Answer: 23.56 nV

Explanation:

Assuming that we apply Ohm's Law to this situation, we know that under this condition, the current resultant, is proportional to the voltage applied, and that the proportionality constant, is called the resistance.

Now, we define electric current, as the passage of a number of charges over time.

In this case, we can say that each singly-ionized potassium ion carries the charge equivalent to the one electron, which is q = 1.6. 10⁻¹⁹ coulombs.

So, as we have 90,000 ions, we will have a total charge as follows:

Q =90.10³. 1.6.10⁻¹⁹ coulombs

Also, we are told that this charge will be moving for 1.1 msec, so we can find the current I as follows:

I = Q/t ⇒ I = 13.09. 10⁻¹² A.

If we know that R= 1.8.10⁹ Ω, we can determine V, applying Ohm's Law, as follows:

V = 13.09. 10⁻¹² A . 1.8.10⁹ Ω = 23.56 nV

3 0

3 years ago

Read 2 more answers

Why are the alkali metals likely to react with group 17 elements?

Rudiy27

Answer:

Because alkali metals are so reactive, they are found in nature only in combination with other elements. They often combine with group 17 elements, which are very “eager” to gain an electron.

Explanation:

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7 0

2 years ago