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3 years ago

An endothermic reaction will start when the required ΔH energy is received from the environment or solution. True or False.

Physics

2 answers:

iren [92.7K]3 years ago

6 0

Answer: A ) ΔH

Explanation:

34kurt3 years ago

5 0

<span>An endothermic reaction will start when the required ΔH energy is received from the environment or solution this is false as the reaction may require energy in excess to start the reaction</span>

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(a) Calculate how much work is required to launch a spacecraft of mass m from the surface of the earth (mass mE, radius RE) and

notsponge [240]

Answer:

(a) The Work need to place spacecraft into low orbit is $Gmm_{E} /2R_{E}$

(b) Additional Work need to place the spacecraft far away from the earth is

$Gmm_{E} /2R_{E}$ .

Explanation:

Explanation is in the following attachments

8 0

3 years ago

A 21.0 kg shopping cart is moving with a velocity of 4.0 m / s. It strikes a 7.0 kg box that is initially at rest. They stick to

jonny [76]

Explanation:

Given that,

Mass of the shopping cart, $m_s=21\ kg$

Initial speed of the shopping cart, $u_s=4\ m/s$

Mass of the box, $m_b=7\ kg$

Initial speed of the box, $u_b=0$ (at rest)

They stick together and continue moving at a new velocity. It is a case of inelastic collision.

(a) The momentum of the shopping cart before the collision is given by :

$p_s=m_s\times u_s\\\\p_s=21\times 4\\\\p_s=84\ kg-m/s$

(b) The momentum of the box before the collision is given by :

$p_b=m_b\times u_b\\\\p_b=7\times 0\\\\p_b=0$

(c) The velocity of the combined shopping cart/box wreckage after the collision is given by using the conservation of momentum as :

$m_su_s+m_bu_b=(m_s+m_b)V\\\\V=\dfrac{m_su_s+m_bu_b}{(m_s+m_b)}\\\\V=\dfrac{21\times 4+0}{(21+7)}\\\\V=3\ m/s$

Hence, this is the required solution.

8 0

3 years ago

If a 4.5 kg object is dropped from a height of 6.0 m, what will be its velocity when it is halfway toward the ground? (Use g = 9

dangina [55]

When an object falls or is dropped from rest it's initial velocity is zero.
Using the equations for a motion in straight line. I can find the time it takes to reach 3.0 m down (half way).
x = vt - 4.9t²
-3 = 0 - 4.9t²
-3/-4.9 = t²
0.6122 = t²
0.7825 sec = t

v = v - gt
v = 0 - 9.8(0.7825)
v = -7.67 m/s
the negative denotes downward direction.

You could also solve the problem using potential and kinetic energy.

Since it starts with maximum PE and gets converted to KE when it hits the ground. mgh = mv²/2
mass cancels, use 3 meters for the halfway distance
-9.8(-3) = v²/2
29.4 * 2 = v²
√(58.8) = 7.67 m/s downwards

7 0

3 years ago

Read 2 more answers

The planet Gallifrey has 2 times the gravitational field strength and 2 times the radius of the Earth.

Alexeev081 [22]

The mass of the planet Gallifrey is 8 times the mass of the Earth.

let the gravitational field of Earth = g
let the radius of the Earth = R
gravitational field of Gallifrey = 2g
radius of Gallifrey = 2R

<h3>What is gravitational potential energy?</h3>

This is the work done in moving an object to a certain distance against gravitational field.

The gravitational field strength of the Earth is given as follows;

$g = \frac{GM}{r^2} \\\\G = \frac{gr^2}{M}$

The gravitational field strength of the Planet Gallifrey is calculated as follows;

$g_2 = \frac{GM_2}{r_2^2}$

$G = \frac{g_2r_2^2}{M_2} \\\\\frac{g_2r_2^2}{M_2} = \frac{gr^2}{M}\\\\M_2gr^2 = Mg_2r_2^2\\\\M_2 = \frac{Mg_2r_2^2}{gr^2} \\\\M_2 = \frac{M \times 2g \times (2r)^2}{gr^2} \\\\M_2 = \frac{M \times 2g \times 4r^2}{gr^2} \\\\M_2 = 8M$

Thus, the mass of the planet Gallifrey is 8 times the mass of the Earth.

Learn more about gravitational field strength here: brainly.com/question/14080810

4 0

2 years ago

Can someone please help me

mario62 [17]

Answer:

GE = ME - $\frac{1}{2} m\,v^2$ , which agrees with option C in your list.

Explanation:

The definition of Mechanical Energy (ME) of a system is the addition of the gravitational potential energy (GE) plus the kinetic energy (KE) of the system:

ME = GE + KE

Given that the KE is: $\frac{1}{2} m\,v^2$ ,

solving for GE in the formula above gives:

GE = ME - KE = ME - $\frac{1}{2} m\,v^2$ , which agrees with option C

8 0

3 years ago