In what phase of matter do molecules vibrate but stay in position?

What is the formula for calculating the efficiency of a heat engine?

Olegator [25]

Explanation:

The efficiency of a heat engine is defined as the ratio of the work output to the heat input into the system.

It is highly impossible to get an engine that is 100% efficient.
A heat engine that is 100% efficient suggests that all the heat input into the system is used to do work completely.
There is no heat loss.

Efficiency = $\frac{work output}{heat input}$ x 100

Efficiency has no unit

Learn more:

Heat brainly.com/question/914750

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7 0

3 years ago

A cannon fires a 0.2 kg shell with initial velocity vi = 9.2 m/s in the direction θ = 46 ◦ above the horizontal. The shell’s tra

Sedbober [7]

Answer:

∆h = 0.071 m

Explanation:

I rename angle (θ) = angle(α)

First we are going to write two important equations to solve this problem :

Vy(t) and y(t)

We start by decomposing the speed in the direction ''y''

$sin(\alpha) = \frac{Vyi}{Vi}$

$Vyi = Vi.sin(\alpha ) = 9.2 \frac{m}{s} .sin(46) = 6.62 \frac{m}{s}$

Vy in this problem will follow this equation =

$Vy(t) = Vyi -g.t$

where g is the gravity acceleration

$Vy(t) = Vyi - g.t= 6.62 \frac{m}{s} - (9.8\frac{m}{s^{2} }) .t$

This is equation (1)

For Y(t) :

$Y(t)=Yi+Vyi.t-\frac{g.t^{2} }{2}$

We suppose yi = 0

$Y(t) = Yi +Vyi.t-\frac{g.t^{2} }{2} = 6.62 \frac{m}{s} .t- 4.9\frac{m}{s^{2} } .t^{2}$

This is equation (2)

We need the time in which Vy = 0 m/s so we use (1)

$Vy (t) = 0\\0=6.62 \frac{m}{s} - 9.8 \frac{m}{s^{2} } .t\\t= 0.675 s$

So in t = 0.675 s → Vy = 0. Now we calculate the y in which this happen using (2)

$Y(0.675s) = 6.62\frac{m}{s}.(0.675s)-4.9 \frac{m}{s^{2} } .(0.675s)^{2} \\Y(0.675s) =2.236 m$

2.236 m is the maximum height from the shell (in which Vy=0 m/s)

Let's calculate now the height for t = 0.555 s

$Y(0.555s)= 6.62 \frac{m}{s} .(0.555s)-4.9\frac{m}{s^{2} } .(0.555s)^{2} \\Y(0.555s) = 2.165m$

The height asked is

∆h = 2.236 m - 2.165 m = 0.071 m

6 0

4 years ago

Read the following passage and find the two errors. Then, choose the answer that

solmaris [256]

Answer:

O pH is a measure of the concentration of H+ ions in a solution of an acid or base. The pH plots

the concentration of solutions in a range from 0-14.

Explanation:

pH is a measure of how acidic/basic water is. The range goes from 0 to 14, with 7 being neutral.

6 0

3 years ago

John is going to use a rope to pull his sister Laura across the ground in a sled through the snow. He is pulling horizontally wi

bulgar [2K]

Answer:

The mass of Laura and the sled combined is 887.5 kg

Explanation:

The total force due to weight of Laura and friction on the sled can be calculated as follows;

$F_T = F_L+F_S$

= (400 + 310) N

= 710 N

From Newton's second law of motion, "the rate of change of momentum is directly proportional to the applied force.

$F_T = \frac{(M_L+M_S)V}{t}$

where;

$M_L$ is mass of Laura and

$M_S$ is mass of sled

Mass of Laura and the sled combined is calculated as follows;

$(M_L+M_S) = \frac{F_T*t}{V}$

given

V = Δv = 4-0 = 4m/s

t = 5 s

$(M_L+M_S) = \frac{710*5}{4}\\\\(M_L+M_S) = 887.5 kg$

Therefore, the mass of Laura and the sled combined is 887.5 kg

4 0

3 years ago

Two billiard balls of equal mass are traveling straight toward each other with the same speed. They meet head-on in an elastic c

Rus_ich [418]

Answer:

0 kg m/s before and after collision

Explanation:

Let m, v be the mass and speed of the 2 balls, respectively, before the collision. Since they have the same mass and same speed but in opposite direction, the total momentum of the system would be:

P = mv - mv = 0 kg m/s

As the collision is elastic. The total momentum after the collision is the same as the total momentum before the collision, which is 0.

5 0

3 years ago