Answer:
B. The presence of an unbalanced force(e.g friction) causes a moving object to stop.
Explanation:
As the friction is that force that can stop the sled upon reaching the levelled surface so the option b is correct.
Answer:

Explanation:
Average velocity is defined as the ratio of total displacement of the motion and total time taken in that motion
here we know that initially the sky diver drops without opening parachute by total displacement 625 m
then she open her parachute and drop another 362 m
so first it took time t = 15 s to drop without open parachute
then it took t = 139 s to drop next displacement
so here total displacement is given as

total time is given as

so average velocity is given as


Answer:
h = 4.04 m
Explanation:
Given that,
Mass of a child, m = 25 kg
The speed of the child at the bottom of the swing is 8.9 m/s
We need to find the height in the air is the child is able to swing. Let the height is h. Using the conservation of energy such that,

Put all the values,

So, the child is able to go at a height of 4.04 m.
Radiation fog is the fog that is formed when the heat absorbed the Earth's surface is released into the atmosphere producing fog. This only occurs when the air is clear and calm. In the center of an anticyclone, the conditions of the air are clear and calm which is favorable for the formation of radiation fog. The center of cyclones, on the other hand, is turbulent and cloudy which prevents the formation of radiation fogs.
<span>The two factors that act on parachutes are gravity and air resistance, which is also called drag. Gravity acts as a force to pull parachutes down to the surface of the Earth, while air resistance generates movement in the opposite direction of the falling parachute, and essentially pushes the parachute upward. hope this helps!:)</span>