Physics Notes for High School
DEDICATED TO HELP STUDENTS EXCEL IN PHYSICS BY GIVING NOTES, MOTIVATION AND RESOURCES ESPECIALLY FOR (O-LEVEL), High School, Secondary School Students. Grade 9 | Grade 10 | Year 9 | Year 10 | Form 4 | Form 5| | This site is best seen using Web version. If this site helps, please consider sharing this in your social media. Thanks heaps! |
Effects of Forces
Application for the principles of momentum conservation
1. Billiard / Pool game
Billiards game uses a ball to hit other balls into holes. The more momentum the cue ball has the greater the momentum force exerted on the target ball / balls.
2. Water hose
Water that jets out from a firemen hose exerts high backward force, hence firemen needs to hold fast the hose to prevent it from moving.
When rowing a boat, the backward force exerted by the rower will result in the same forward force being produced.
4. Jet engine
The hot gas and vapour ejected at the exhaust of a jet engine will produce an upward and forward force, equal to the force exerted by the hot gas.
A mixture of oxygen and hydrogen are burned up in the combustion chamber. This creates a very high pressure and force which is expelled at the bottom of the rocket. As a result, an upward force of similar magnitude is produced.
Linear momentum collision problem calculations 2
1. A toy truck with a mass of 3 kg was moving at 3 ms-1 and hit with another toy truck of 1 kg and was moving with a velocity of 1 ms-1, in the opposite direction. After collision, both trucks moved together in the same direction, calculate the common velocity of the two objects after collision.
m1u1 + m2u2 = (m1+ m2)v
(3)(3) + (1)(-1) = (3+1)v
9 – 1 = 4v
v = 2 ms-1
2. A hunter shot a 100g bullet from a 1.5kg gun. If the bullet travelled 200 ms-1 after being triggered, what is the backward jerk of the gun. (Think final backward velocity of the gun).
Total initial momentum = Total final momentum = 0
m1u1 + m2u2 = 0
1.5(v) + 0.1(200) = 0 ß make sure to convert 100g to kg
1.5v +20 = 0
v = - 13.3 ms-1 ß Value is negative because gun moved in opposite direction
3. A trolley of mass 2 kg was in a stationary condition, before a 5 g sticky plasticine was thrown into it with a velocity of 500 ms-1. After hitting the trolley, the plasticine sticks into it. Calculate the final velocity of both the trolley and plasticine?
Use the classic formula of momentum conservation
m1u1 + m2u2 = m1v1 + m2v2
0.005 (500) + 2 (0) = (0.005+ 2)v
2.5 = 2.005v
v = 1.245 ms-1