Everything Science Grade 10

21.7 CHAPTER 21. MOTION IN ONE DIMENSION

here is a list for reference purposes:

~u = initial velocity ( m·s−^1 ) att= 0 s

~v = final velocity (m·s−^1 ) at timet

~s = displacement (m)

In this book we will use the first convention.

FACT

Galileo Galilei of
Pisa, Italy, was the
first to determined the
correct mathematical
law for acceleration:
the total distance
covered, starting from
rest, is proportional
to the square of the
time. He also con-
cluded that objects
retain their velocity
unless a force – often
friction – acts upon
them, refuting the
accepted Aristotelian
hypothesis that ob-
jects “naturally” slow
down and stop unless
a force acts upon
them. This principle
was incorporated into
Newton’s laws of
motion (1st law).

~vf = ~vi+~at (21.1)

∆~x = (~vi+ 2 ~vf)t (21.2)

∆~x = ~vit+^12 ~at^2 (21.3)

vf^2 = vi^2 + 2~a∆~x (21.4)

The questions can vary a lot, but the following method for answering them will always

work. Use this when attempting a question that involves motion with constant acceleration.

You need any three known quantities (~vi,~vf,∆~x,tor~a) to be able to calculate the fourth

one.

Problem solving strategy:

1. Read the question carefully to identify the quantities that are given. Write them down.

2. Identify the equation to use.Write it down!!!

3. Ensure that all the values are in the correct units and fill them in your equation.

4. Calculate the answer and check your units.

Example 7: Equations of motion

QUESTION

A racing car is travelling North. It accelerates uniformly covering a distance of 725

m in 10 s. If it has an initial velocity of 10 m·s−^1 , find its acceleration.

SOLUTION

Step 1:Identify what information is given and what is asked for

426 Physics: Mechanics