Answer:
Stationary
20N
Explanation:
From the graph, we see that the body traveling is on a fixed position. Therefore, it is a stationary body.
The graph given is a position - time curve.
This curve depict a body changing position with given time.
Since the line of the curve is on a single position, the body is not changing position with the passage of time therefore, it is a stationary object.
B. 20N
From Newton's third law of motion we understand that "action and reaction force are equal but oppositely directed".
Since the person is exerting a force of 20N on the balance.
So, the reaction force by the balance is 20N upward.
The force of gravity produces acceleration in all C. freely falling objects and this is known as acceleration due to gravity
Explanation:
A body is said to be in free fall when there is only one force acting on the body: the force of gravity.
Gravity is a force that acts downward, i.e. towards the Earth's centre.
If we are near the Earth's surface, the magnitude of the force of gravity on a body is given by

where:
m is the mass of the body
g is known as the acceleration of gravity , whose value near the Earth's surface is
).
We can apply Newton's second law on an object in free-fall, to find its acceleration. In fact, we have:

where F is the force acting on the body and a is its acceleration.
Solving for the acceleration,

And substituting F,

Therefore, every object in free-fall accelerates at
towards the ground.
Learn more about free fall here:
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Answer:
none of the above
Explanation:
The actual answer is '91 protons'. In fact, the beta decay of the thorium-234 is the following:

where inside the nucleus of Thorium (90 protons), a neutron turns into an electron (the beta particle) + a proton. Therefore, the resulting nucleus (which is Protoactinium) has a total of 90+1 = 91 protons.
So, the correct answer would be '91 protons'.