**
SPH 4U1**

**
Physics Grade 12**

**
Unit 2: Kinematics (How Things Move)**

**
Note 2: Speed and Velocity**

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Reference Text Section 1.1

*Recall Definitions:*

**Scalar **– magnitude and a unit (no direction)- time,
distance, speed

**Vector **– point of reference, magnitude, unit &
direction – positions, displacement, velocity

**Speed** – rate of change of distance with time

**Displacement **– the change of positions (final
position – the intial position)

**Velocity** – rate of change of position with time

**Instantaneous Velocity** – speed at one point in time
together with the direction it is moving in at that time.

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**Example 1:** A person jogs around a circular 800m
track in 6 minutes. Calculate

(i) the average speed

(ii) the average velocity

Solution: Convert 6 minutes to seconds 6.0 min.* 60.0 s/min. = 360.0 s

(i) average speed =

(ii) average velocity =

**Example 2:** A clock has a 2^{nd} hand that is
12.0 cm long. Find the following:

(i)
Average speed of the tip of the 2^{nd} hand

(ii) Instantaneous velocity as it passes the 6 & 9 on the clock face

(iii) Average velocity in moving from the 3 to the 12 on the clock

Solution:

(i)

(ii) (recall inst velocity is speed & dir’n at that point in time)

Speed is constant so

Answer: As it passes the 6 the inst. **
Velocity is 1.3 cm/s [LEFT] **

Answer: As it passes the 9 the
inst. **Velocity is 1.3 cm/s [UP]**

(iii) Find the displacement of the 2^{nd} hand from 3 to 12

**Do Section 1.1 Questions
Page 17**