pls answer the question
Answers
Answer:
C)a)Momentum is the product of mass and velocity of a body, for a body mass never be zero but velocity can be zero if a body is at rest, So if a body is at rest its momentum is zero but if it is in rest at a height it possesses gravitational potential energy hence mechanical energy
b)Given that,
Power =1200W=1.2kWh
Time = 30 min / day × 30 days =0.5h×30= 15 h
Energy =Power×Time=1.2×15= 18kWh.
D)a)The Kilowatt
A kilowatt is simply a measure of how much power an electric appliance consumes—it’s 1,000 watts to be exact. You can quickly convert watts (W) to kilowatts (kW) by diving your wattage by 1,000:
1,000W 1,000 = 1 kW.
The Kilowatt-Hour
A kilowatt-hour measures the energy an appliance uses in kilowatts per hour. For example, if you clean your floors with a 1,000-watt vacuum cleaner for one hour, you consume 1 kWh of energy.
Your kilowatt-hour consumption factors in how many watts your appliances use and how often you use them. When you see kWh on your monthly energy bill, it’s a measurement of your electric appliances’ wattage and the amount of time you use them.
b) mass=30kg
force= mass×acceleration
= 30×9.8
=294N
after a complete rotation the displacement is zero
work done= force×displacement
= 294×0
=0Joules
the work done by the girl 0 joules.
c)When a body is dropped from a certain height, its potential energy gradually changes into kinetic energy. On reaching the ground, the whole of its potential energy gets converted into kinetic energy.
d)Law of conservation of energy states that the energy of a system is always constant. In other words, we can say that energy can neither be created nor destroyed. In the case of a freely falling body, it is the mechanical energy of the system that is conserved. Therefore, E=K+U=constant.