Answer:
Ff = u M g frictional force where u = .62
1/2 M v^2 kinetic energy of water bottle at release
Ff * d = 1/2 M v^2 = u M g d work to stop equals initial kinetic energy
v^2 = 2 u g d = 2 * .62 * 9.8 * 12 = 146 m^2 / s^2
v = 12.1 m/s
Poor visibility, difficulties in colour perception, lessened colour contrast vision due to darker shadows and reduced peripheral vision, these are the reasons why one has to be extra careful while driving during hours of sunrise, sunset and night time.
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Explanation:
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Sunrise, sunset and night time are parts of the day with minimal or absolutely no presence of sunlight. To safely navigate roads, we require enough light in order to detect presence of other vehicles, signs and pedestrians. Less sunlight during sunrise and sunset light the sky but makes the roads and vehicles have a darker, less bright view. The contrast between colours is the least, making it difficult to identify objects and see clearly.
A rising or a setting sun can also lead to glares on the driver’s view and thus obstruct it. Since a change in ambient light is observed, our eyes need to adjust with this change and this isn’t spontaneous. Night time driving has headlight glares from approaching vehicles and reduced surrounding visibility. The eyes switching for vision adaptability from dark to bright light if vehicles approach and pass by is not a quick action. Hence the driver’s vision is compromised in every such case and this may lead to accidents.
The efficiency of the engine at the given useful energy and input energy is 28%.
The given parameters:
- <em>Input energy of the engine, = 125 J</em>
- <em>Useful energy of the engine, 35 J</em>
The efficiency of the engine is defined as the ratio of the output energy (useful energy) to the input energy and it is calculated as follows;
Thus, the efficiency of the engine at the given useful energy and input energy is 28%.
Learn more about efficiency of engine here: brainly.com/question/6751595
Answer:
Microwave: Radiation
Water: Conduction, convection & radiation.
Explanation:
- When we heat a food using microwave then the water content of the food is only heated by the microwave.
- Microwaves make the molecules of water vibrate frequently with a frequency closer to the frequency of microwaves and this increases the kinetic energy of the molecules which produces heat in the water molecules this heat then propagates to the whole food by conduction and convection, but the heat enters the food only via radiation.
Now when the food item is kept into warm water then the molecules closer to the food heat the food by conduction through direct energy transfer by lattice vibrations and when they become cooler than the mass of water all around then due to density difference they settle down and their place is occupied by warmer molecules around in the fluid leading to convection.
Radiation of energy from a mass occurs continuously irrespective of the medium present there. So the heat of water also enters the food by radiation of energy from the water molecules.
Answer:
a. the amount of work done on a system is dependent of pathway
Explanation:
The first law of thermodynamics states that the change in internal energy of a system equals the net heat transfer into the system minus the net work done by the system.
ΔU = Q - W
Where;
Q, the net heat transfer into the system depends on the pathway
W, the net work done by the system also depends on the pathway
But, ΔU, the change in internal energy is independent of pathway
Therefore, the correct option is "A"
a. the amount of work done on a system is dependent of pathway
