m=2 t = 2000 kg
Vo=0
Vk= 54 km/h = 15 m/s
t=15 s
Fn=?
s=?
Fn=m*a
a=(Vk-Vo)/t
Fn=m*(Vk-Vo)/t
Fn=2000*(15-0)/15
Fn= 2 kN
s=Vo*t+0,5*a*t²
s=0,5*a*t²
s=0,5*(Vk-Vo)*t
s=0,5*(15-0)*15
s=112,5 m
[tex]dane:\\m = 2 \ t = 2 \ 000 \ kg\\v_{o} = 0\\t = 15 \ s\\v = 54\frac{km}{h} = 54\cdot\frac{1000 \ m}{3600 \ s} = 15\frac{m}{s}\\szukane:\\F = ?\\s = ?[/tex]
Rozwiązanie
Siła działania silnika autobusu F:
[tex]a = \frac{\Delta v}{t} = \frac{v-v_{o}}{t} = \frac{v}{t} = \frac{15\frac{m}{s}}{15 \ s} = 1\frac{m}{s^{2}}\\\\Z \ II \ zadady \ dynamiki\\\\a = \frac{F}{m} \ \ /\cdot m\\\\F = m\cdot a\\\\F = 2000 \ kg\cdot1\frac{m}{s^{2}}\\\\F = 2 \ 000 \ N = 2 \ kN[/tex]
Droga rozpędzania s:
[tex]dla \ \ v_{o} = 0\\\\s = \frac{1}{2}at^{2}\\\\s = \frac{1}{2}\cdot1\frac{m}{s^{2}}\cdot(15 \ s)^{2}\\\\s = 112,5 \ m[/tex]