Answer:
a) 
Now we can replace the velocity for t=1.75 s

For t = 3.0 s we have:

b) 
And we can find the positions for the two times required like this:
And now we can replace and we got:

Explanation:
The particle position is given by:

Part a
In order to find the velocity we need to take the first derivate for the position function like this:

Now we can replace the velocity for t=1.75 s

For t = 3.0 s we have:

Part b
For this case we can find the average velocity with the following formula:

And we can find the positions for the two times required like this:
And now we can replace and we got:

Answer:
The radius of a chamber is 2.36 meters.
Explanation:
Given that,
The outer wall moves at a speed of 2.72 m/s.
Mass of the person, m = 75.1 kg
The person feels a force of 235 N force pressing against his back. The force acting on the person is centripetal force. It is given by the below formula :

r is the radius of a chamber


r = 2.36 meters
So, the radius of a chamber is 2.36 meters. Hence, this is the required solution.
Answer: direction
Explanation:
Given
The resultant vector of a force gives us information regarding the direction of the resultant force.
If there are multiple forces acted in a different direction then, the resultant vector describes the direction of the resultant force.
Gravity is the only one, since there's no air resistance.
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'.