Answer:
The correct option is;
D) The force exerted on the astronaut by Earth is equal to the force exerted on Earth by the astronaut
Explanation:
According to Newton's third law of motion, in nature, for every action, there is an equal and opposite reaction, such that if a first object exerts a certain amount of force on a second object, the second object will exert a force of equal magnitude and opposite direction to that exerted by the first object
Therefore, the gravitational force exerted by Earth on the astronaut, is equal to the force exerted by the astronaut on Earth.
Answer:
The starting position of the runner.
Explanation:
When you look at the graph, you can see that the first point on the graph is twenty on the y-axis.
The runner starts at twenty, and ends at thirty.
Therefore, the runner starts at twenty on the y-axis, so it's the starting position of the runner.
Answer:
you can see it in the picture
Answer:

Explanation:
Four people standing on the ground each of mass and usually this questions have to find the final angular velocity

The radius 
Angular velocity 
The moment of inertia total is 
Momento if inertia


Angular momentum

Solve to w2



Answer:
a) It is moving at
when reaches the ground.
b) It is moving at
when reaches the ground.
Explanation:
Work energy theorem states that the total work on a body is equal its change in kinetic energy, this is:
(1)
with W the total work, Ki the initial kinetic energy and Kf the final kinetic energy. Kinetic energy is defined as:
(2)
with m the mass and v the velocity.
Using (2) on (1):
(3)
In both cases the total work while the objects are in the air is the work gravity field does on them. Work is force times the displacement, so in our case is weight (w=mg) of the object times displacement (d):
(4)
Using (4) on (3):
(5)
That's the equation we're going to use on a) and b).
a) Because the branch started form rest initial velocity (vi) is equal zero, using this and solving (5) for final velocity:


b) In this case the final velocity of the boulder is instantly zero when it reaches its maximum height, another important thing to note is that in this case work is negative because weight is opposing boulder movement, so we should use -mgd:

Solving for initial velocity (when the boulder left the volcano):

