Page 28 - Focus TG4 KSSM (Physics) Terbitan Penerbitan Pelangi Sdn Bhd

Physics Form 4 Chapter 2 Force and Motion I

1. The procedure is modified with both the trolleys A and B each pulling a ticker tape separately.
This is required as the trolleys are moving separately after collision.
2. The resultant tape is as shown below.
Direction of motion

After collision Before collision
During
Velocity = v collision Velocity = u
Figure 2.60
3. The experiment is repeated with
(a) 1 trolley colliding with 2 stationary trolleys,
(b) 2 trolleys colliding with 1 stationary trolley, and
(c) 3 trolley colliding with 1 stationary trolley.
Chapter
2 Results: Table 2.6

Before collision After collision

u Total momentum, Total momentum
m 1 m 2 v 1 v 2
m 1 u m 1 v 1 + m 2 v 2
1 1
1 2
2 1
3 1

Conclusion:
The total momentum before collision is the same as that of after collision. The hypothesis is accepted.

EXAMPLE 2.15

Figure 2.62 shows two rocks moving towards each Let v be the velocity of the rocks after collision.
other along a straight line. After colliding with each Total momentum before collision
other, the two rocks lump together. = (2 000 × 750) + [500 × (–2 000)]
750 m s –1 2 000 m s –1 = 500 000 kg m s –1
Total momentum after collision
A
B = (2 000 + 500) × v
= 2 500v
500 kg According to the principle of conservation of
2 000 kg
Figure 2.61 momentum, the total momentum before and after
the collision are the same.
Calculate the speed of the rocks after the collision.
Therefore,
Solution 2 500v = 500 000
–1
v A = 750 m s v B = –2 000 m s –1 v = 200 m s –1
m A = 2 000 kg m B = 500 kg

44

02 FOC PHYSICS F4 3P.indd 44 29/01/2020 1:39 PM