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2 years ago

a runner starts from rest and has an acceleration of 3 m/s^2. How fast is she running after 1.1 seconds

1 answer:

8 0

Acceleration x time = velocity

Since you're given acceleration and time, just plug the values into the equation.

3 $\frac{m}{s^{2}}$ x 1.1 s = ?

Solve that equation, and remember your velocity should be in m/s.

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( Find the value of the following in ms-1<br> 54kmhr

Darina [25.2K]

Answer:

54 × 5/18 = 15m/s

Explanation:

to convert km/hr to m/s you multiply by 5/18

6 0

1 year ago

A thermometer initially reading 212F is placed in a room where the temperature is 70F. After 2 minutes the thermometer reads 125

frez [133]

Answer:

91.3°F

Explanation:

Let T be the temperature of the thermometer at any time

T∞ be the temperature of the room = 70°F

T₀ be the initial temperature of the thermometer = 212°F

And m, c, h are all constants from the cooling law relation

From Newton's law of cooling

Rate of Heat loss by the cake = Rate of Heat gain by the environment

- mc (d/dt)(T - T∞) = h (T - T∞)

(d/dt) (T - T∞) = dT/dt (Because T∞ is a constant)

dT/dt = (-h/mc) (T - T∞)

Let (h/mc) be k

dT/(T - T∞) = -kdt

Integrating the left hand side from T₀ to T and the right hand side from 0 to t

In [(T - T∞)/(T₀ - T∞)] = -kt

(T - T∞)/(T₀ - T∞) = e⁻ᵏᵗ

(T - T∞) = (T₀ - T∞)e⁻ᵏᵗ

Inserting the known variables

(T - 70) = (212 - 70)e⁻ᵏᵗ

(T - 70) = 142 e⁻ᵏᵗ

At t = 2 minute, T = 125°F

125 - 70 = 142 e⁻ᵏᵗ

55/142 = e⁻ᵏᵗ

- kt = In (55/142) = In (0.3873)

- k(2) = - 0.9485

k = 0.4742 /min

At time t = 4 mins

kt = 0.4742 × 4 = 1.897

(T - 70) = 142 e⁻ᵏᵗ

e^(-1.897) = 0.15

T - 70 = 142 × 0.15 = 21.3

T = 91.3°F

7 0

3 years ago

A certain capacitor, in series with a resistor, is being charged. At the end of 10 ms its charge is half the final value. The ti

vichka [17]

To solve this problem we will apply the expression of charge per unit of time in a capacitor with a given resistance. Mathematically said expression is given as

$q(t) = e^{-\frac{t}{(R*C)}}$

Here,

q = Charge

t = Time

R = Resistance

C = Capacitance

When the charge reach its half value it has passed 10ms, then the equation is,

$\frac{1}{2}*q_{final} = e^{-\frac{0.01}{(R*C)}}$

$Ln(\frac{1}{2}) = -\frac{0.01}{RC}$

$- RC = \frac{0.01}{Ln(1/2)}$

$RC = 0.014s$

We know that RC is equal to the time constant, then

$T = RC = 0.014s = 14ms$

Therefore the time constant for the process is about 14ms

5 0

3 years ago

You take a trip from your home to Mali, a very poor country in western Africa. How is the water usage you observe there likely t

Harlamova29_29 [7]

Answer:

It is likely that the citizens have very limited water for agriculture and personal uses and it is stored in their homes, while in the U.S we have water ready at the moment we need it and can access it with faucets.

Explanation:

4 0

2 years ago

What happens to the ray of light when it travels from glass to water?

vodomira [7]

Glass and water are thicker and heavier than air. They are said to be 'denser' than air. What happens is that light slows down when it passes from the less dense air into the denser glass or water. This slowing down of the ray of light also causes the ray of light to change direction.

7 0

2 years ago