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7. Option D. 8.4×10¯⁴ m/s North.

8. Option B. 2 m/s

Explanation:

7. Determination of the speed of the snail.

The following data were obtained from the question:

Distance travalled (d) = 15 m

Time (t) = 300 mins

Speed (S) =?

Next, we shall convert 300 mins to secs. This can be obtained as follow:

1 min = 60 secs

Therefore,

300 mins = 300 × 60 = 18000 secs

Finally, we shall determine the speed of the snail as follow:

Distance travalled (d) = 15 m

Time (t) = 18000 secs

Speed (S) =?

Speed = Distance travelled /time

Speed = 15 / 18000

Speed = 8.3×10¯⁴ m/s

Since the snail travelled due north, the speed is therefore 8.3×10¯⁴ m/s North.

8. Determination of speed of the runner.

The following data were obtained from the question:

Distance travalled = 8 m

Time = 4 secs

Speed =?

Speed = Distance travalled / time

Speed = 8/4

Speed = 2 m/s

Therefore, the speed of the runner is 2 m/s.

a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation:

force is mass*acceleration.

we have a very small mass: 11.4*0.001 kg

if we want 0.035n of force, we need an acceleration:

0.035 = 11.4*0.001*a

a = 0.035/(11.4*0.001) m/s^2