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Alona [7]
3 years ago
8

A ball of 10kg falls from rest from a height of 150m, Neglating air resistance, calculate its kinetic energy after falling a dis

tance of 40m. Take g=10m/s
Physics
1 answer:
GaryK [48]3 years ago
3 0

Answer: 3920\ J

Explanation:

Given

mass of ball m=10 kg

It is placed at a height of 150 m

It is dropped from the height and allowed to free fall for 40 m

Velocity acquired by the ball during this fall is given by v^2-u^2=2as

Insert u=0, a=g

\Rightarrow v^2-0=2\times 9.8\times 40\\\Rightarrow v=\sqrt{784}\\\Rightarrow v=28\ m/s

Kinetic energy at this instant

K.E.=\dfrac{1}{2}\times 10\times 28^2\\\\\Rightarrow K.E.=3920\ J

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An ideal heat engine absorbs 97.2 kJ of heat and exhausts 83.8 kJ of heat in each cycle. What is the efficiency of the engine?
r-ruslan [8.4K]

Answer:

13.7%

Explanation:

Given that,

Heat absorbed by the engine = 97.2 kJ

Heat exhausted by the engine in each cycle = 83.8 kJ

We need to find the efficiency of the engine. It is calculated by the formula.

\eta=1-\dfrac{Q_e}{Q_a}\\\\=1-\dfrac{83.8}{97.2}\\\\=0.137\\\\=13.7\%

so, the efficiency of heat engine is 13.7%.

5 0
3 years ago
Which option lists a form of potential energy followed by a form of kinetic energy?
Nadusha1986 [10]

Answer:

Magnetic energy and electromagnetic energy form of potential energy followed by a form of kinetic energy.

(B) is correct option.

Explanation:

Given that,

Lists a form of potential energy followed by a form of kinetic energy

We know that,

Sound energy :

The movement of energy through object it is called sound energy. When a object produced vibration by force then it moves in wave.

Sound wave is example of kinetic energy.

Nuclear energy :

The store energy in the nucleus of the atom it is called nuclear energy. This energy released when occurs fusion and fission.

Nuclear energy is the example of potential energy

Magnetic energy :

Magnetic energy is a type of potential energy which is depend on distance and position in the magnetic field.

Electromagnetic energy :

Electromagnetic energy is light energy. it is type of kinetic energy.

Gravitational energy :

Gravitational energy is a type of potential energy. It is an energy related with gravity or gravitational force.

Elastic energy :

The store energy in elastic object it is called elastic energy. This energy is a type of potential energy.

Electrical energy :

The movement of electrons is called electrical energy. When electrons move through a wire then it is are called electricity. Electrical energy is type of kinetic energy.

Hence, Magnetic energy and electromagnetic energy form of potential energy followed by a form of kinetic energy.

(B) is correct option.

4 0
3 years ago
Read 2 more answers
True or false the refraction of a wave is how many wavelengths pass a fixed point each second
Ksenya-84 [330]
False. That description fits the wave's 'frequency'. 
It has nothing to do with refraction.
8 0
3 years ago
Read 2 more answers
A circular loop of flexible iron wire has an initial circumference of 165cm , but its circumference is decreasing at a constant
ArbitrLikvidat [17]

Answer:

emf induced is 0.005445 V and direction is clockwise because we can see area is decrease and so that flux also decrease so using right hand rule direction of current here clockwise

Explanation:

Given data

initial circumference = 165 cm

rate = 12.0 cm/s

magnitude = 0.500 T

tome = 9 sec

to find out

emf induced and direction

solution

we know emf in loop is - d∅/dt    ........1

here ∅ = ( BAcosθ)

so we say angle is zero degree and magnetic filed is uniform here so that

emf = - d ( BAcos0) /dt

emf = - B dA /dt     ..............2

so  area will be

dA/dt = d(πr²) / dt

dA/dt = 2πr dr/dt

we know 2πr = c,

r = c/2π = 165 / 2π

r  = 26.27 cm

c is circumference so from equation 2

emf = - B 2πr dr/dt    ................3

and

here we find rate of change of radius that is

dr/dt = 12/2π = 1.91  10^{-2}cm/s

so when 9.0s have passed that radius of coil = 26.27 - 191 (9)

radius = 9.08 10^{-2} cm

so now from equation 3 we find emf

emf = - (0.500 )  2π(9.08 10^{-2} )   1.91  10^{-2}

emf = - 0.005445

and magnitude of emf = 0.005445 V

so

emf induced is 0.005445 V and direction is clockwise because we can see area is decrease and so that flux also decrease so using right hand rule direction of current here clockwise

4 0
3 years ago
A child on a tricycle is moving at a speed of 1.40 m/s at the start of a 2.25 m high and 12.4 m long incline. The total mass is
goblinko [34]

Answer:

The work done by the child as the tricycle travels down the incline is 416.96 J

Explanation:

Given;

initial velocity of the child, v_i = 1.4 m/s

final velocity of the child, v_f = 6.5 m/s

initial height of the inclined plane, h = 2.25 m

length of the inclined plane, L = 12.4 m

total mass, m = 48 kg

frictional force, f_k = 41 N

The work done by the child is calculated as;

\Delta E_{mech} = W - f_{k} \Delta L\\\\W = \Delta E_{mech}  + f_{k} \Delta L\\\\W = (K.E_f - K.E_i) + (P.E_f - P.E_i) + f_{k} \Delta L\\\\W = \frac{1}{2} m(v_f^2 - v_i^2) + mg(h_f - h_i) + f_{k} \Delta L\\\\W = \frac{1}{2} \times 48(6.5^2 - 1.4^2) + 48\times 9.8(0-2.25) + (41\times 12.4)\\\\W = 966.96  \ - \ 1058.4 \ + \ 508.4\\\\W = 416.96 \ J

Therefore, the work done by the child as the tricycle travels down the incline is 416.96 J

5 0
3 years ago
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