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Physics Form 4 Chapter 2 Force and Motion I

Analysis of Motion
EXAMPLE 2.6
1. A ticker timer is an apparatus used to study
the motion of an object within a short period A trolley pulled a ticker tape through a ticker timer
of time. while moving down an inclined plane. Figure 2.17
shows the ticker tape produced.
2. Figure 2.15 shows a ticker timer connected to
an a.c. power supply.

12 cm
Power supply Figure 2.17
a.c.12 V POWER SUPPLY
FUSE 10 12 Volts 1
8 plus
O 6 Determine the average velocity of the trolley.
Ticker timer 4 AC 2 0 0
I OVLD DC
Solution
Ticker
tape Displacement = 12 cm
There are 10 spaces between the dots,
Chapter
2 Vibrating bar Therefore, time taken = 10 × 0.02 = 0.2 s
Displacement
Average velocity =
Time taken
Figure 2.15 Ticker timer = 12 cm = 60 cm s –1
0.2 s
3. A carbonised ticker tape is passed through the
ticker timer and is pulled by a moving object. EXAMPLE 2.7
A trolley is pushed Length/cm
4. When the a.c. power supply is switched on, to move up the slope 4.5
the vibrating bar vibrates 50 times per second of an inclined plane. 4.0
(following the frequency of the power supply Figure 2.18 shows the 3.5
3.0
which is 50 Hz). Each time the vibrating bar arrangement of the 2.5
hits the tape, a dot is produced on the tape. ticker tapes. Each strip 2.0
1.5
5. The period of time between 2 adjacent dots is consists of 5 ticks or 0.1 1.0
0.5
known as 1 tick. second. Determine the 0.2 0.4 0.6 0.8 t /s
acceleration of the trolley. Figure 2.18
Solution
Average initial velocity of the trolley,
4.5 cm
Dot 1 tick u = = 45.0 cm s –1
Figure 2.16 1 tick for carbonised ticker tape 0.1 s
Average final velocity of the trolley,
1.5 cm
6. A ticker timer can be used to determine v = 0.1 s = 15.0 cm s –1
(a) time, Time taken, t = (4 – 1) × 0.1
(b) displacement, = 0.3 s
(c) average velocity, Therefore, acceleration, a = v – u
(d) acceleration, and t
(e) type of motion = 15.0 – 45.0
of an object. 0.3
= –100 cm s –2
Because the acceleration has a negative value,
therefore the trolley experienced a deceleration
with the magnitude of 100.0 cm s .
–2

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