In particle kinematics, we measure the acceleration of the particle. For this, an observer is taken as a reference point. Generally we consider the observer as in origin of a co-ordinate system. The place where observer is placed is known as frame of reference.
Newton's laws only work in the inertial frame of reference. Inertial frame is a frame of reference whose acceleration is zero. But, if you are observing the motion of an object from non-inertial frame, you need to add and extra force on the system under observation which is known as pseudo force.
15) a
16) b
17) a
Hope this helps
By definition, the power is given by:

Where,
F: Force
d: distance traveled
t: time
The power units is watts.
Substituting values we have:

Making the corresponding calculations we have:
Answer:
he uses 63 watts of power:
Without friction, we would not be able to stop walking since we would just keep slipping like on ice.
Without friction, objects would just slip and fall with a simple blow of air
And finally without friction we wouldn't be able to use machinery like cars and etc since they would just fly off
Hope this helps!
(tell me if im right)