9 the one plz tell fast as possible

23. What mass of water will give up 240 calories<br> when its temperature drops from 80°C to 68°C?

svp [43]

Answer:

20g

Explanation:

Given parameters:

Quantity of heat = 240calories

Initial temperature = 80°C

Final temperature = 68°C

Unknown:

Mass of water = ?

Solution;

To solve this problem, we use the expression:

Q = m c (t₂ - t₁)

Q is the quantity of heat

m is the mass

c is the specific heat = 1 cal/g°C

t₂ is the final temperature

t₁ is the initial temperature

Insert the parameters and solve;

Change in temperature is an absolute value

240 = m x 1 x (68 - 80)

m = 20g

3 0

3 years ago

According to ohms law if you don't change the value of the resistor and you double the voltage in a circuit the amount of curren

padilas [110]

Answer: D (doubled)

According to ohm's law

I = V/R ,

V = IR ; R = constant and V is doubled

From the equation

V is directly proportional to the current, and it is given that R is constant ;

2V = 2I. R since R = constant

Hence I is doubled.

5 0

4 years ago

The two conducting rails in the drawing are tilted upwards so they each make an angle of 30.0° with respect to the ground. The v

dolphi86 [110]

Answer:

The current flows through the rod is 14.9 A.

Explanation:

Given that,

Magnetic field = 0.045 T

Mass of aluminum rod = 0.19 kg

Length = 1.6 m

Angle = 30.0°

We need to calculate the force

Using resolving force

$F\cos\theta=mg\sin\theta$

$F=mg\tan\theta$

Put the value into the formula

$F=0.19\times9.8\times\tan30$

$F=1.075\ N$

We need to calculate the current flows through the rod

Using formula of magnetic force

$F=iLB$

$i=\dfrac{F}{LB}$

Put the value into the formula

$i=\dfrac{1.075}{1.6\times0.045}$

$i=14.9\ A$

Hence, The current flows through the rod is 14.9 A.

8 0

3 years ago

A 1.0-kilogram rubber ball traveling east at 4.0 meters per second hits a wall and bounces back toward the west at 2.0 meters pe

Mrrafil [7]

Answer:

8 J and 2 J

Explanation:

Given that,

Mass of the rubber ball, m = 1 kg

Initial speed of the rubber ball, u = 4 m/s (in east)

Final speed of the rubber ball, v = -2 m/s (in west)

We need to find the kinetic energy of the ball before it hits the wall, the kinetic energy of the ball after it bounces off the wall.

Initial kinetic energy,

$K_i=\dfrac{1}{2}mv^2\\\\K_i=\dfrac{1}{2}\times 1\times (4)^2\\\\K_i=8\ J$

Final kinetic energy,

$K_f=\dfrac{1}{2}mv^2\\\\K_f=\dfrac{1}{2}\times 1\times (2)^2\\\\K_f=2\ J$

So, the initial kinetic energy is 8 J and the final kinetic energy is 2 J.

8 0

3 years ago

Two resistors have resistances R(smaller) and R(larger), where R(smaller) < R(larger). When the resistors are connected in se

just olya [345]

Answer:

1.61ohms and 4.39ohms

Explanation:

According to ohm's law which States that the current (I) passing through a metallic conductor at constant temperature is directly proportional to the potential difference (V) across its ends. Mathematically, E = IRt where;

E is the electromotive force

I is the current

Rt is the effective resistance

Let the resistances be R and r

When the resistors are connected in series to a 12.0-V battery and the current from the battery is 2.00 A, the equation becomes;

12 = 2(R+r)

Rt = R+r (connection in series)

6 = R+r ...(1)

If the resistors are connected in parallel to the battery and the total current from the battery is 10.2 A, the equation will become;

12 = 10.2(1/R+1/r)

Since 1/Rt = 1/R+1/r (parallel connection)

Rt = R×r/R+r

12 = 10.2(Rr/R+r)

12(R+r) = 10.2Rr ... (2)

Solving equation 1 and 2 simultaneously to get the resistances. From (1), R = 6-r...(3)

Substituting equation 3 into 2 we have;

12{(6-r)+r} = 10.2(6-r)r

12(6-r+r) = 10.2(6r-r²)

72 = 10.2(6r-r²)

36 = 5.1(6r-r²)

36 = 30.6r-5.1r²

5.1r²-30.6r +36 =

r = 30.6±√30.6²-4(5.1)(36)/2(5.1)

r = 30.6±√936.36-734.4/10.2

r = 30.6±√201.96/10.2

r = 30.6±14.2/10.2

r = 44.8/10.2 and r = 16.4/10.2

r = 4.39 and 1.61ohms

Since R+r = 6

R+1.61 = 6

R = 6-1.61

R = 4.39ohms

Therefore the resistances are 1.61ohms and 4.39ohms

5 0

3 years ago