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3 years ago

An Olympic athlete runs a 400 m race in 50 s. What is her average speed?

Physics

1 answer:

timurjin [86]3 years ago

4 0

Answer:

Explanation:

distance = 400 m

time = 50 s

speed = distance / time

= 400 / 50

= 8 m/s

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A hot iron ball of mass 200 g is cooled to a temperature of 22°C. 6.9 kJ of heat is lost to the surroundings during the process.

qaws [65]

Heat lost or gained, H = mc(θ₂ - θ₁)
Where m = mass, c = Specific heat capacity, θ₂= final temperature, θ₁ = initial temperature

m = 200g, c = 0.444 J/g°C, θ₁ = 22 °C (Since it was cooled).

H = 6.9 kj = 6.9 *1000J = 6900 J

6900 = 200*0.444* (θ₂ - 22)

6900/(200*0.444) = θ₂ - 22

77.70 = θ₂ - 22

θ₂ - 22 = 77.7

θ₂ = 77.7 + 22 = 99.7

So initial temperature before cooling ≈ 100°C . Option C.

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Taking right movement to be positive means leftward movement is negative.
Hence we have a deceleration of
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$t = 4s$
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Using this 'suvat' equation
$v = u + at$
we can determine the initial velocity

$3.0= u + -2.5(4)$

$3.0+2.5(4)=u$

$13.0 = u$

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Which of the following should be useful to show the percentage of total growth in plants exposed to various pollutants?

marishachu [46]

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vodomira [7]

Answer:

$V = IR$

Explanation:

Required

Which equation represents ohm's law?

Literally, ohm's law implies that current (I) is directly proportional to voltage (V) and inversely proportional to resistance (R).

Mathematically, this can be represented as:

$I\ \alpha\ \frac{V}{R}$

Convert the expression to an equation

$I\ =\ \frac{V}{R}$

Multiply both sides by R to make V the subject

$I\ * R\ =\ \frac{V}{R} * R$

$I\ * R\ =V$

Reorder

$V = I\ * R$

$V = IR$

Option (a) is correct; Others are not

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Answer:

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