Everything Science Grade 10

CHAPTER 21. MOTION IN ONE DIMENSION 21.7

use Equation 21.2:

∆~x = (~vi+ 2 ~vf)t

∆~x = 10 + 0s (8)

∆~x = 40m

Step 5:Write the final answer

The total distance that the truck covers isdAB+dBC= 5 + 40 = 45

meters. The child is 50 meters ahead. The truck will not hit the child.

Chapter 21 | Summary

See the summary presentation ( Presentation: VPgjl at http://www.everythingscience.co.za)

• A reference point is a point from where you take your measurements.


• A frame of reference is a reference point with a set of directions.


• Your position is where you are located with respect to your reference point.


• The displacement of an object is how far it is from the reference point. It is the
  shortest distance between the object and the reference point. It has magnitude and
  direction because it is a vector.


• The distance of an object is the length of the path travelled from the starting point to
  the end point. It has magnitude only because it is a scalar.


• Speed (v) is the distance covered (D) divided by the time taken (∆t):

v=∆Dt

• Average velocity (~vav) is the displacement (∆~x) divided by the time taken (∆t):

~vav=∆∆~xt

• Instantaneous speed is the speed at a specific instant in time.


• Instantaneous velocity is the velocity at a specific instant in time.

Physics: Mechanics 435