B a bar magnet has a north and a south pole.
Answer:
955.5N
Explanation:
The normal force is given by the difference between the centripetal force and gravity at the top of the loop:

mass m = 65kg
radius of the loop r = 4m
velocity v = ?
g = 9.8 m/s²
To find the centripetal force, you need to find the velocity of the car at the top of the loop.
Use energy conservation:

At the top of the hill:

At the top of the loop:

Setting both energies equal and canceling the mass m gives:

Solving for v:

Using v in the first equation:

Answer:
C) Contact
Explanation:
The magnet requires almost direct <u>contact</u> with the fridge to start its magnetic properties.
Answer:
16km/h
Explanation:
Vt=20km/h ---train speed
Vd=4km/h
Donas speed relative to ground is:
Vrd=Vt-Vd
Donas is moving in opposite direction of train .
Vrd=20km/h-4km/h
Vrd=16km/h
Since both heat and work can be measured and quantified, this is the same as saying that any change in the energy of a system must result in a corresponding change in the energy of the surroundings outside the system. In other words, energy cannot be created or destroyed.