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sveta [45]
3 years ago
10

Which describes a train’s acceleration if it changes speed from 25 m/s to 10 m/s in 240 s? positive acceleration no acceleration

negative acceleration
Physics
1 answer:
OLEGan [10]3 years ago
3 0

To understand acceleration, you need to know speed and velocity.

Why?

Acceleration is the change in velocity, and the velocity equation is:

velocity = distance / time     Units: (m/s)

If a change in position means an object has a velocity, then that means that a change in velocity has an acceleration (I recommend you look at the graphs, it will help a lot to understand the relationship between each).

Now that we have some background, lets use it to answer the problem!

The change in velocity is from 25 m/s to 10 m/s, and we have a time. Lets plug it into the (average) acceleration equation so we can visualize it better!

The symbol delta means "change" : Δ

a = Δv / Δt

expanded to:

a = vf - vi / tf - ti  

(vf = velocity final, vi = velocity initial, tf = time final, ti = time initial)

So if the train's speed went from 25 m/s to 10 m/s, then that means that 10 m/s is our final velocity and 25 m/s is the initial:

a = 10 - 25 / 240

a = -15 / 240

a = -0.0625 m/s^2

Since we ended up with a negative number, it means that the train has a negative acceleration!!!!!

The fast way to do this:

25 m/s is bigger than 10 m/s, so that means that to go from 25 m/s to 10 m/s you have to slow down--otherwise known as putting on your brakes. So if the change in speed is negative then the acceleration will be negative.

In other words, if your final speed is less than your initial speed then your acceleration would be negative.

Sorry for the long explanation! I hope you never struggle with this again though!

Hope it helped,

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3 years ago
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An engine causes a car to move 10 meters with a force of 100 N. The engine produces 10,000 J of energy. What is the efficiency o
kodGreya [7K]

Answer:

Part A

The efficiency of the engine is 10%

Part B

The change in internal energy is 300 J

Part C

The change in volume is 1 m³ which is one cubic meter

Explanation:

Part A

Efficiency is defined as the ratio of energy output to energy input;

The given parameters are;

The distance the car is moved, d = 10 meters

The force which moves the car, F = 100 N

The amount of energy produced by the engine = 1,000 J

Therefore, we have;

The energy output to the car = The work done on the car = Force applied to the car, F × The distance the car moves, d;

∴ The energy output to the car by the engine = F × d = 100 N × 10 m = 1,000 J

The energy input from the engine = The energy produced by the engine = 10,000 J

The efficiency of the engine = (The energy output)/(The energy input)= 1,000J/10,00J = 0.1

The efficiency in percentage = 0.1 × 100 = 10 %

The efficiency of the engine = 10%

Part B

The amount of heat added to the substance, ΔQ = 1,000J

The amount of work the substance does on the atmosphere, W = 700 J

The change in internal energy, ΔU is given as follows;

ΔQ = W + ΔU

∴ ΔU = ΔQ - W

For the substance, we have;

The change in internal energy, ΔU = 1,000 J - 700 J = 300 J

Part C

The work done by the piston, W = 1,000 J

The pressure, in the piston, P = 1,000 Pa = constant

The work done by the piston in a constant pressure process, W = P × ΔV

Where;

W = The work done

P = The constant pressure applied

ΔV = The change in volume = V₂ - V₁

V₂ = The final volume

V₁ = The initial volume

∴The change in volume ΔV = W/P = 1,000 J/(1,000Pa) = 1 m³

The change in volume ΔV = 1 m³

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Explanation:

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Explanation:

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