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3 years ago

A car drives on a highway with a speed of 68mi/hr. What is the speed in km/hr?

Physics

1 answer:

spin [16.1K]3 years ago

3 0

Answer:

Speed in km/hr will be 109.412 km/hr

Explanation:

We have given speed of the car on a highway = 68 mi/hr

We have to find the speed in km/hr

For this first we have to change mi to km

We know that 1 mile = 1.609 km

Speed is the ratio of distance and time

So 68 mi/hr $=68\times 1.609km/hr=109.412km/hr$

So the speed in km/hr will be 109.412 km /hr

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An object is dropped from a height of 25 meters. At what velocity will it hit the ground?

Goryan [66]

You can use Vf^2-Vi^2 = 2ax

Vf^2 - 0 = 2(9.81)(25)

Or you can use energy

mgh = 1/2mv^2

2gh =v^2

Same thing

6 0

3 years ago

An ideally efficient heat pump delivers 1000 J of heat to room air at 300 K. If it extracted heat from 260 K outdoor air, how mu

choli [55]

Answer:

Wnet, in, = 133.33J

Explanation:

Given that

Pump heat QH = 1000J

Warm temperature TH= 300K

Cold temperature TL= 260K

Since the heat pump is completely reversible, the combination of coefficient of performance expression is given as,

From first law of thermodynamics,

COP(HP, rev) = 1/(1-TL/TH)

COP(HP, rev) = 1/(1-260/300)

COP(HP, rev) = 1/(1-0.867)

COP(HP, rev) = 1/0.133

COP(HP, rev) = 7.5

The power required to drive the the heat pump is given as

Wnet, in= QH/COP(HP, rev)

Wnet, in = 1000/7.5

Wnet, in = 133.333J. QED

So the 133.33J was the amount heat that was originally work consumed in the transfer.

Extra....

According to the first law, the rate at which heat is removed from the low temperature reservoir is given as

QL=QH-Wnet, in

QL=1000-133.333

QL=866.67J

5 0

3 years ago

suppose you use three different scales to weigh bag of oranges one scale says the bag weighs 2.1 lbs a second says it weighs 2.2

Ber [7]

Answer:

It would be 2.2 if you have to round the five to the one but if your not rounding the number, it'd be 2.1.

Explanation:

4 0

2 years ago

Suppose astronomers find an earthlike planet that is twice the size of Earth (that is, its radius is twice the radius of Earth).

JulijaS [17]

Answer:

4 times the mass of Earth

Explanation:

$M_1$ = Mass of Earth

$M_2$ = Mass of the other planet

r = Radius of Earth

2r = Radius of the other planet

m = Mass of object

The force of gravity on an object on Earth is

$F=\frac{GM_1m}{r^2}$

The force of gravity on an object on the other planet is

$F=\frac{GM_2m}{(2r)^2}$

As the forces are equal

$\frac{GM_1m}{r^2}=\frac{GM_2m}{(2r)^2}\\\Rightarrow M_1=\frac{M_2}{4}\\\Rightarrow M_2=4M_1$

So, the other planet would have 4 times the mass of Earth

6 0

3 years ago

A particle moving uniformly along the x axis is located at 11.3m at 0.588s and at 3.38m at 4.67s. Find its displacement during t

Yakvenalex [24]

Displacement = (distance between start and end points) in the direction of (direction from start to end point). Distance = (11.3-3.38)= 7.92 m. Direction = the negative 'x' direction.

5 0

3 years ago

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