Answer:
(1) A hot drink cooling to room temperature.
(2) The combustion of natural gas.
Explanation:
The spontaneous process is the process in which there is a release of energy and moves towards lower energy and a more thermodynamically stable energy state. All the natural processes are spontaneous.
There are two processes which are spontaneous in the given question are:
(1) A hot drink cooling to room temperature: In this, there is a decrease in energy and also it is a natural process and we know that all the natural processes are spontaneous.
(2) The combustion of natural gas: The fire is an example of an exothermic reaction. The combustion is a combination of a decrease in energy and an increase in entropy. So, this process occurs spontaneously.
Answer:
The importance of international bureau of weights and measures are;
1. to bring unification of measurement system.
2. to establish and preserve fundamental international prototypes.
3. to verify national standards, etc.
Given :
Initial speed , u = 0 m/s .
Final speed , v = 91 km/h = 25.28 m/s .
To Find :
a) Average acceleration .
b ) Assuming the motorcycle maintained a constant acceleration, how far is it from the traffic light after 3.3 s .
Solution :
a )
We know ,by equation of motion :

b)
Also , by equation of motion :

Hence , this is the required solution .
The object's speed will not change.
In fact, after the astronaut throws the object, no additional forces will act on it (since the object is in free space). According to Newton's second law:

where the first term is the resultant of the forces acting on the body, m is the mass of the object and a its acceleration, we see that if no forces act on the object, then the acceleration is zero. Therefore, the acceleration of the object is zero, and its velocity remains constant.