1. یو لات شوی فوټبال په ځمکه کې په داسې زاویه کې پریږدي چې θ = 30 ويo with the initial velocity of 10 m/s. Ball’s ډله = 0.1 کیلوګرامه سرعت د جاذبې له امله 1 دی0 م / س2. Determine (a) The د جاذبې احتمالي انرژي at the highest point (b) The highest point or the maximum height
پیژندل شوی:
وزن (متر) = 0.1 کیلوګرامه
The initial velocity (vo) = ۲ متره/ ثانیې
Angle = 30o
د جاذبې قوې له امله سرعت (g) = 10 m/s2
حل:
(a) The gravitational potential energy

Calculate the horizontal component (vox) and the vertical component (voy) of initial velocity.

vox = ویo کاس θ = (۲۰)(د ۳۰ په اندازهo) = (10)(0.5√3) = 5√3 m/s
voy = ویo د ګناه θ = (۱۰)(ګناه ۶۰o) = (10)(0.5) = 5 m/s
لومړنۍ میخانیکي انرژي
د لومړنیو میخانیکي انرژي (MEo) = متحرکه انرژي (KE)
MEo = KE = ½ m vo2 = ½ (۱)(۰.۱)2 = ½ (0.1)(100) = ½ (10) = 5 Joule
The final mechanical energy
Kinetic energy at the highest point :
KE = ½ m vox2 = ½ (0.1)(5√3)2 = ½ (0.1)((25)(3)) = ½ (0.1)(75) = 3.75 Joule
Principle of conservation of mechanical energy
The initial mechanical energy (MEo) = the final mechanical energy (MEt)
KE = PE + KE
5 = EP + 3.75
PE = 5 – 3.75 = 1.25 Joule
The gravitational potential energy at the highest point is 1.25 Joule.
(b) The highest point or the maximum height
PE = m g h
1.25 = (0.1)(10) h
1.25 = h
The maximum height is 1.25 meters.
2. A 0.1-kg ball projected horizontally with initial velocity vo = 10 m/s from a building 10 meter high. Acceleration due to gravity is 10 m/s2. Determine ball’s kinetic energy when it hits the ground.
پیژندل شوی:
وزن (متر) = 0.1 کیلوګرامه
لومړنی سرعت (vo) = ۲ متره/ ثانیې
د جاذبې قوې له امله سرعت (g) = 10 m/s2
The change in height (h) = 10 – 2 = 8 m
SE busca: kinetic energy at 2 meters above the ground
حل:
The gravitational potential energy (PE) = m g h = (0.1)(10)(10) = 10 Joule
The initial kinetic energy (KE)= ½ m vo2 = ½ (۱)(۰.۱)2 = ½ (0.1)(100) = ½ (10) = 5 Joule
The final kinetic energy = the initial gravitational potential energy + the initial kinetic energy = 10 + 5 = 15 Joule
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