# Questions on the basic principles of physics.

1. Nov 8, 2007

Really isn't involving problems, just principles of physics.

What are the units of velocity?

Im aware of m/s, but I hear there are more.

What is the value of "G"?

If an object starts from rest and travels a distance d in t sec, what equation may be used to find its acceleration?

Really all I need help on.

2. Nov 8, 2007

### Bill Foster

Average velocity is the change in unit distance per the change in unit time. (m/s, mph, feet/sec. km/h, etc).

Instantaneous velocity is the rate of change in position per the rate of change per unit time. Same units.

The value of g is 9.8 $$\frac{m}{s^2}$$ or 32.2 $$\frac{ft}{s^2}$$

Equation of motion:

$$x=x_0+vt+\frac{1}{2}at^2$$ Solve for a

3. Nov 8, 2007

I dont think you properly understood the question.

4. Nov 8, 2007

And I know the value of G is 9.8 we

but It would be 980cm/m2

right

5. Nov 8, 2007

### Bill Foster

Centimeters per meter-squared? No. In centimeters, it would be $$\frac{cm}{s^2}$$

6. Nov 8, 2007

### catkin

Velocity could be measured in any distance units divided by any time units.

The acceleration caused by Earth's gravitational field, at the surface of the Earth, is normally denoted by g (not G) and is 9.81 meters per second per second.

If your object is accelerating at a constant rate then the equation to use is
d = 0.5 at^2
a = 2d / t^2

7. Nov 8, 2007

Yra I know it is 9.80 meters, but they want to convert it into centimeters. So it would b 980?

8. Nov 8, 2007

### Bill Foster

Yes. Use google as a calculator. Put in the following "9.8 meters to cm", click "search" and you get out the following: 9.8 meters = 980 centimeters

It even does automatic unit conversions. Put in "9.8 m + 32.2 ft", click "search and get back:

(9.8 meters) + (32.2 feet) = 19.61456 meters

"50 mph + 10 m/s" "search"

(50 mph) + (10 (m / s)) = 32.35200 m / s

Pretty damn cool, huh?

9. Nov 8, 2007

### Feldoh

Velocity is loosely a change in a position (distance) divided by the time interval that it took to change position.

So it will always be a distance over a time. Big G is called the gravitational constant( $$6.673*10^-11 \frac{m^3 s}{kg}$$). Little g is acceleration due to gravity ($$GM/R^2$$). On the surface of the earth we can roughly measure it to (9.80m/s^2)