a). for velocity, you must have a number, a unit, and a direction.
Yes. This one isn't bad. The 'number' and the 'unit' are the speed.
b). the si units for velocity are miles per hour.
No. That's silly.
'miles' is not an SI unit, and 'miles per hour'
is only a speed, not a velocity.
c). the symbol for velocity is .
You can use any symbol you want for velocity, as long as
you make its meaning very clear, so that everybody knows
what symbol you're using for velocity.
But this choice-c is still wrong, because either it's incomplete,
or else it's using 'space' for velocity, which is a very poor symbol.
d). to calculate velocity, divide the displacement by time.
Yes, that's OK, but you have to remember that the displacement
has a direction, and so does the velocity.
RADIATION BELTS....... I think but it should be radiation belt
Well, first of all, the car is not moving at a uniform velocity, because,
on a curved path, its direction is constantly changing. Its speed may
be constant, but its velocity isn't.
The centripetal force on a mass 'm' that keeps it on a circle with radius 'r' is
F = (mass) · (speed)² / (radius).
For this particular car, the force is
(2,000 kg) · (25 m/s)² / (80 m)
= (2,000 kg) · (625 m²/s²) / (80 m)
= (2,000 · 625 / 80) (kg · m / s²)
= 15,625 newtons .
