Answer:
a = 12.8 m/s^2
Explanation:
To find the centripetal acceleration you use the following formula:
(1)
v: tangential speed of the rock = 17.90mph
r: radius of the orbit = 1000cm/2 = 500cm = 0.5m
You first change the units of the tangential velocity in order to replace the values of v and r in the equation (1):

Then, you use the equation (1):

hence, the centripetal acceleration is 12.8 m/s^2
Complete question:
At a particular instant, an electron is located at point (P) in a region of space with a uniform magnetic field that is directed vertically and has a magnitude of 3.47 mT. The electron's velocity at that instant is purely horizontal with a magnitude of 2×10⁵ m/s then how long will it take for the particle to pass through point (P) again? Give your answer in nanoseconds.
[<em>Assume that this experiment takes place in deep space so that the effect of gravity is negligible.</em>]
Answer:
The time it will take the particle to pass through point (P) again is 1.639 ns.
Explanation:
F = qvB
Also;

solving this two equations together;

where;
m is the mass of electron = 9.11 x 10⁻³¹ kg
q is the charge of electron = 1.602 x 10⁻¹⁹ C
B is the strength of the magnetic field = 3.47 x 10⁻³ T
substitute these values and solve for t

Therefore, the time it will take the particle to pass through point (P) again is 1.639 ns.
Answer:hot air
Explanation:Hot air goes up, so when you put it in a hot air balloon fire is placed at the oppening to creat hot air and lift the balloon! :)