The equivalent resistance of several devices connected in parallel is given by

where

are the resistances of the various devices. We can see that every time we add a new device in parallel, the term

increases, therefore the equivalent resistance of the circuit

decreases.
But Ohm's law:

tells us that if the equivalent resistance decreases, the total current in the circuit increases. The power dissipated through the circuit (and so, the heat produced) depends on the square of the current:

therefore if there are too many devices connected in parallel, this can be a problem because there could be too much power dissipated (and too much heat) through the circuit.
Consider a long train moving at speed v. Now consider a passenger throwing a ball inside this train, towards the back of the train, with same velocity v (but in the opposite direction of the train movement).
- A passenger inside the train will see the ball moving with speed v
- For an observer outside the train, however, the ball will appear as still. In fact, for him the ball will have a speed v (given by the movement of the train) -v (velocity of the ball but moving in the opposite direction), so the net velocity will be v+(-v)=0.
Answer:
As the skydiver falls to the Earth, she experiences positive acceleration only due to gravity.
Explanation:
As the skydiver falls to the Earth, she experiences friction in the form of air resistance which tries to slow her down and is proportional to the her velocity. So it cannot have a positive acceleration as it acts in opposite direction to slow her down.
Inertia during skydiving is experienced when we open an parachute, the parachute slows down the speed of are descent hence changing our inertia of motion with a velocity.
Only the Earth's, gravitational field has an positive acceleration as it pulls us towards the Earth, hence increasing our velocity.
Answer:
-4,651.42N
Explanation:
Since we are not asked what to find, we can calculate the force applied by the track as shown;
F = ma
F = m(v-u)/t
Substitute the given value
F = 4400(7.6-52)/42
F = 4400(-44.4)/42
F = -4,651.43N
Hence the required force is -4,651.42N