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-Dominant- [34]
4 years ago
13

Determine which heat transfers below are due to the process of conduction. I) You walk barefoot on the hot street and it burns y

our toes. II) When you get into a car with hot black leather in the middle of the summer and your skin starts to get burned. III) A flame heats the air inside a hot air balloon and the balloon rises. IV) A boy sits to the side of a campfire. He is 10 feet away, but still feels warm. A) I and II B) III and IV C) I, II, and IV D) II, III, and IV
Physics
2 answers:
Rudik [331]4 years ago
3 0

I) You walk barefoot on the hot street and it burns your toes.

The road is in direct contact with your skin. Thermal energy from the road will transfer to the bottom of your feet, then to the rest of your body. This is an example of conduction.


II) When you get into a car with hot black leather in the middle of the summer and your skin starts to get burned.

Just like in the previous example, the hot leather is in direct contact with your skin (I guess if you're going to drive naked). Thermal energy from the leather will transfe to your skin, then to the rest of your body. This is also conduction.


III) A flame heats the air inside a hot air balloon and the balloon rises.

The flame heats air directly at the bottom of the balloon. The warm air expands and becomes less dense. This will rise and let the unheated, denser air in the balloon fall down toward the flame. This is an example of the convection cycle.


IV) A boy sits to the side of a campfire. He is 10 feet away, but still feels warm.

The campfire heats air directly nearby. The warm air expands and moves away from the fire in all directions, leaving behind unheated, denser air to be heated up. Some of the warm air reaches the boy. This is another example of convection.


The answer is A) 1 and 2.

Shkiper50 [21]4 years ago
3 0

Explanation:the correct answer is A

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George walks to a friend's house. He walks 750 meters North, then realizes he walked
Sauron [17]

Answer:

I think you are looking for the velocity, so the answer is 38.5 m/s

Explanation:

Velocity is giving by displacement/time. North will be positive and South will be negative, George travels 750 meters then travels -250 meters his displacement is then 750 - 250 or 500 meters. Divide that by 13 seconds to get 38.5 m/s.

4 0
3 years ago
A child slides down a snow‑covered slope on a sled. At the top of the slope, her mother gives her a push to start her off with a
kirill [66]

Answer:

θ = 13.16 °

Explanation:

Lets take mass of child = m

Initial velocity ,u= 1.1 m/s

Final velocity ,v=3.7 m/s

d= 22.5 m

The force due to gravity along the incline plane = m g sinθ

The friction force = (m g)/5

Now from work power energy

We know that

work done by all forces = change in kinetic energy

( m g sinθ - (m g)/5 ) d = 1/2 m v² - 1/2 m u²

(2  g sinθ - ( 2 g)/5 ) d = v² -  u²

take g = 10 m/s²

(20 sinθ - ( 20)/5 ) 22.5 = 3.7² -  1.1²

20 sinθ - 4 =12.48/22.5

θ = 13.16 °

5 0
3 years ago
A hoop, a solid disk, and a solid sphere, all with the same mass and the same radius, are set rolling without slipping up an inc
nadya68 [22]

Answer:

Solution is given in the attachments

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3 years ago
A 1.50-m cylindrical rod of diameter 0.500 cm is connected to a power supply that maintains a constant potential difference of 1
nydimaria [60]

Answer:

a) 1.06*10^-5

b) 0.00105 °C^-1

Explanation:

Given that

Length of the cylinder, L = 1.5 m

Radius of the cylinder, r = 0.25 cm

Voltage across the rod, V = 15 V

I• at Temperature T• = 20° C is 18.5 A

I at Temperature T = 90° C is 17.2 A

See attachment for calculations

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3 years ago
A person driving her car at 43 km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow
siniylev [52]

Answer:

If she hits the brakes, she will travel 13m before stopping. If she hits the gas, she will travel 28 before the light turns red. She should try to stop

Explanation:

To know how far she will travel before stopping, we need to use a kinematic formula which initial final velocity (Vf), initial velocity (V0), acceleration (a) and distance traveled(x):

V_{f}^{2}=V_{0} ^{2} +2ax

The moment in which she stops is when the final velocity equals zero. In this case, initial velocity is 43km/h=12m/s, and its maximum deceleration is -5.4m/s^2. Plugging in these values and solving for x:

0^2=(12m/s)^2+2(-5.4m/s)x\\x=13m

She will travel 13m before stopping

If she hits the gas, we need another kinematic formula, which relates distance traveled, initial speed, time (t) and acceleration.

x=v_{0}t+0.5a*t^2

If we know her car can accelerate from 43km/h=12m/s to 70km/h=19m/s in 8.1 s, we can know its acceleration:

a=\frac{19m/s-12m/s}{8.1s}=0.86m/s^2

In this case, the time before the light turns red is 2.0s. Plugging in all those values:

x=12m/s*2s+0.5*0.86m/s^2*(2s)^2=28m

If she hits the gas, she will travel 28m before the light turns red. She won't even reach the intersection, so she would try to stop.

5 0
3 years ago
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