Complete question:
A 45-mH ideal inductor is connected in series with a 60-Ω resistor through an ideal 15-V DC power supply and an open switch. If the switch is closed at time t = 0 s, what is the current 7.0 ms later?
Answer:
The current in the circuit 7 ms later is 0.2499 A
Explanation:
Given;
Ideal inductor, L = 45-mH
Resistor, R = 60-Ω
Ideal voltage supply, V = 15-V
Initial current at t = 0 seconds:
I₀ = V/R
I₀ = 15/60 = 0.25 A
Time constant, is given as:
T = L/R
T = (45 x 10⁻³) / (60)
T = 7.5 x 10⁻⁴ s
Change in current with respect to time, is given as;

Current in the circuit after 7 ms later:
t = 7 ms = 7 x 10⁻³ s

Therefore, the current in the circuit 7 ms later is 0.2499 A
Answer:
648.40N
Explanation:
Centripetal acceleration is the acceleration of an object around a circular path. Centripetal for e acting on the combined mass is expressed as:
F = ma
F = mv²/r
m is the mass of the object = 143kg
v is the linear velocity = 13.8m/s
r is the radius = 42.0m
Substitute the given parameters into the formula;
F = 143*13.8²/42
F = 27,232.92/42
F = 648.40N
Hence the magnitude of the centripetal force acting on the combined mass is 648.40N
F is force, m is mass and a<span> is acceleration. The math behind this is quite simple. If you double the force, you double the acceleration, but if you double the mass, you cut the acceleration in half.</span>