First of all, we need to write the First Law of thermodynamics assigning the correct sign convention:
where
is the change in internal energy of the system
Q is the heat absorbed/released
W is the work done
and the signs are assigned based on whether there is an increase in the internal energy or not. Therefore:
Q is positive if it is absorbed by the system (because internal energy increases)
Q is negative if it is released by the system (because internal energy decreases)
W is negative if it is done by the system on the surrounding (because internal energy decreases)
W is positive if it is done by the surrounding on the system (because internal energy increases)
Using these definitions, we can now fill the text of the question:
When a system is heated, heat is ABSORBED by the system. The amount of heat added is given a POSITIVE sign. When a system is cooled, heat is RELEASED by the system. The amount of heat is given a NEGATIVE sign. If a gas expands, it must push the surrounding atmosphere away. Thus, work is done BY the system and is given a NEGATIVE sign. If a gas is compressed, then work is done ON the system. This work is given a POSITIVE sign.
Answer:
P = 0.7 [kg*m/s]
Explanation:
The amount of linear momentum is defined as the product of mass by Velocity. This way you have the following equation:
P = m*v
P = momentum [kg*m/s]
m = mass = 140 [g] = 0.140 [kg]
v = velocity = 5 [m/s]
P = 0.140*5
P = 0.7 [kg*m/s]
PART A)
By Snell's law we know that
here we know that
now from above equation we have
so it will refract by angle 39.3 degree
PART B)
Here as we can see that image formed on the other side of lens
So it is a real and inverted image
Also we can see that size of image is lesser than the size of object here
Here we can use concave mirror to form same type of real and inverted image
PART C)
As per the mirror formula we know that
so image will form at 30 cm from mirror
it is virtual image and smaller in size
Answer:
Explanation:
Given that,
Mass of the cricket ball, m = 0.2 kg
Initial speed of the ball, u = 3 m/s
Final speed of the ball, v = -15 m/s (opposite direction)
To find,
The change in the ball's momentum and the impulse.
Solution,
The change in momentum of the ball is given by :
Negative sign shows that the momentum is acting in opposite direction. We know that the change in momentum of an object is called impulse. So, the impulse of the ball is also 3.6 kg-m/s.
Answer:
<em>metal conducts heat better than wood.</em>
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Explanation:
Metals are generally good conductors of heat, and they usually conduct heat at a relatively rapid rate. Inside the room with a uniform temperature, a metal when touched will rapidly conduct the heat from your hand, leaving your hand with a cooler feeling. Wood on the other hand is a poor heat conductor, so the heat is not conducted from your hand fast enough to cool it up to the point that your hand feels cool.
