Answer:

Explanation:
We know that speed is given by dividing distance by time or multiplying length and frequency. The speed of the father will be given by Lf where L is the length of the father’s leg ad f is the frequency.
We know that frequency of simple pendulum follows that 
Now, the speed of the father will be
while for the child the speed will be 
The ratio of the father’s speed to the child’s speed will be

Answer:
(c) 97 dB sound intensity level
Explanation:
We have given the intensity of the loud car horn 
We know that 
Now the sound intensity level is given by
, which is nearly equal to 97
So the sound intensity level will be 97 dB
So option (c) will be the correct option
Answer: work must be done on the system (Option A)
Explanation:
The second law of thermodynamics is the fundamental law of nature; it states that energy can be transferred from cold objects to hot objects only, if work is done on the system. If energy is added to the system then as a result the thermal energy would increase. Second law of thermodynamics is used to determine whether a process is spontaneous or not. Moreover,the second law of thermodynamics is also used in refrigerators.
Answer:
0 (there is no speed)
Explanation:
If an object is at rest, it is not moving, and it doesn't have a speed, so the speed is zero.