1). Walking / Driving
If there were no static friction between the soles of your shoes and the ground, then you could move your feet back and forth but your body would never go anywhere.
Same for using tires to move a car, a bus, a bicycle or a motorcycle.
2). Sleeping
If there were no static friction between your jammies and the sheet, you would slide right off of the bed whenever there was the slightest breeze of air in the room.
Answer:
The correct answer is intensity.
Explanation:
The principle of overload is a basic sports fitness training concept which means that in order to improve, athletes must continually work harder as they their bodies adjust to existing workouts. Thus, overloading also plays a role in skill learning.
Now, since erhen wants to increase his mile run from eight to six minutes by run some sandy hills near his home, it means the principle at work is making his training runs more intense for better speed results. Thus the principle at work is intensity because he is trying to do something that makes him run faster.
Answer:

Explanation:
The equation for centripetal acceleration is
.
We know the wheel turns at 45 rpm, which means 0.75 revolutions per second (dividing by 60), so our frequency is f=0.75Hz, which is the inverse of the period T.
Our velocity is the relation between the distance traveled and the time taken, so is the relation between the circumference
and the period T, then we have:

Putting all together:

Answer:
Part a)

Part b)

Part c)
distance L is independent of the mass of the sphere
Explanation:
Part a)
As we know that rotational kinetic energy of the sphere is given as

so we will have

so we will have




Part b)
By mechanical energy conservation law we know that
Work done against gravity = initial kinetic energy of the sphere
So we will have



Part c)
by equation of energy conservation we know that

so here we can see that distance L is independent of the mass of the sphere