Question

oblicz zadania, najlepiej na dzis

1. oblicz v
a) s=5m t=2s
b) s=20km t=30min
2. oblicz s
a)v=20m/s t=5s
b)v=5km/h t=15min
3. oblicz a
a) v¹= 20m/s vz=5m/s t=5s
b) deltav=18km/h t=60s​

Answer 1

Ruch jednostajny

1.

[tex]a)\\s = 5 \ m\\t = 2 \ s\\\\v = \frac{s}{t}\\\\v = \frac{5 \ m}{2 \ s}=\boxed{2,5\frac{m}{s}}[/tex]

[tex]b)\\s = 20 \ km\\t = 30 \ min = 0,5 \ h\\\\v = \frac{s}{t}\\\\v = \frac{20 \ km}{0,5 \ h} = \boxed{40\frac{km}{h}}[/tex]

2.

[tex]a)\\v = 20\frac{m}{s}\\t = 5 \ s\\\\s = v\cdot t\\\\s = 20\frac{m}{s}\cdot5 \ s = \boxed{100 \ m}[/tex]

[tex]b)\\v = 5\frac{km}{h}\\t = 15 \ min = \frac{15}{60} \ h = \frac{1}{4} \ h\\\\s = v\cdot t\\\\s = 5\frac{km}{h}\cdot\frac{1}{4} \ h = \frac{5}{4} \ km = \boxed{1,25 \ km}[/tex]

Ruch jednostajnie zmienny

3.

Ruch jednostajnie opóźniony.

[tex]a)\\v_1 = 20\frac{m}{s}\\v_2 = 5\frac{m}{s}\\t = 5 \ s\\\\a = \frac{\Delta v}{t} = \frac{v_1-v_2}{t}\\\\a = \frac{20\frac{m}{s}-5\frac{m}{s}}{5 \ s} = \frac{15\frac{m}{s}}{5 \ s} = \boxed{3\frac{m}{s^{2}}}[/tex]

Odp. Wartośc przyspieszenia wynosi 3 m/s². Przyspieszenie to jest zwrócone przeciwnie do wektora prędkości.

[tex]b)\\\Delta v = 18\frac{km}{h} = 18\cdot\frac{1000 \ m}{3600 \ s} = 5\frac{m}{s}\\t = 60 \ s\\\\a = \frac{\Delta v}{t}\\\\a = \frac{5\frac{m}{s}}{60 \ s} =0,08(3)\frac{m}{s^{2}}\approx\boxed{0,083\frac{m}{s^{2}}}[/tex]