Efficiency or 
is calculated by formula: 
where 
also efficiency has no unit.
Now put in the data and calculate the efficiency.
The efficiency of the machine is 0.8
If you want to get percentage just multiply by 100 and you get 80%
Hope this helps.
r3t40
Answer:
Dear user,
Answer to your query is provided below
Acceleration is zero because of no change in velocity.
Explanation:
Remember that velocity is a vector quantity and a vector can change in 3 ways
•Magnitude only
•Direction only
•Both magnitude and direction.
Now the magnitude of velocity (speed) can stay constant while the direction is changing. This is the case in circular motion.
In the question above, it is mentioned that the girl is moving along a straight road. Therefore no change in direction of velocity.
Answer:
the mass of water is 0.3 Kg
Explanation:
since the container is well-insulated, the heat released by the copper is absorbed by the water , therefore:
Q water + Q copper = Q surroundings =0 (insulated)
Q water = - Q copper
since Q = m * c * ( T eq - Ti ) , where m = mass, c = specific heat, T eq = equilibrium temperature and Ti = initial temperature
and denoting w as water and co as copper :
m w * c w * (T eq - Tiw) = - m co * c co * (T eq - Ti co) = m co * c co * (T co - Ti eq)
m w = m co * c co * (T co - Ti eq) / [ c w * (T eq - Tiw) ]
We take the specific heat of water as c= 1 cal/g °C = 4.186 J/g °C . Also the specific heat of copper can be found in tables → at 25°C c co = 0.385 J/g°C
if we assume that both specific heats do not change during the process (or the change is insignificant)
m w = m co * c co * (T eq - Ti co) / [ c w * (T eq - Tiw) ]
m w= 1.80 kg * 0.385 J/g°C ( 150°C - 70°C) /( 4.186 J/g°C ( 70°C- 27°C))
m w= 0.3 kg
B. Electrical energy
Among the choices given, the type of energy associated with
electric currents is electrical energy. By its definition, electric current is
the flow of charged particles through a conductor or a conduction medium, for
example, a wire. Basically, it involves electricity. It is similar to water current
but instead of water molecules, charged particles move down a conductor. These
charged particles are mostly electrons which move freely and at random. When
all the free electrons move in the same direction, a current is created.
