Jawaban Gerak Lurus

1.       E              Diket : v = 72 km/jam = 20 m/s

S = 15 km = 15000 m

                                Ditanya : t = … ?

                                Dijwb :   s = v . t

                                                15000 = 20 . t

                                                t = 15000 / 20 = 750 s

                                                t = 750 / 60 = 12,5 menit

2.       B             Diket : s = 200 m

t = 20 s

                                Ditanya : v = …?

                                Jawab : s = v . t

                                                200 = v . 20

                                                v = 200 / 20

 v = 10 m/s

3.       C             Diket : s₁ = 5 km

s₂ = 60 km

t₁ = 4 menit

                                Dit : t₂ = ..?

                                Dijwb : s₁ / t₁ = s₂ / t₂

5 / 4 = 60 / t₂

                                                t₂ = 48 menit

4.       F              Diket : v₀ = 0 m/s

t = 5 s

a = 4 m/s²

                                Dit : s = ..?

                                Dijwb : s = v_o.t + ½.a.t²

s = 0.5 + ½.4.5²

s = 50 m

5.       B             Diket : Δs_X =  80– 10 = 70 m

Δs_Y = –70 – (10) = – 80 m

Δt = 10 s

                                Dit : v_X  dan v_Y = ..?

                                Dijwb : v_X  = Δs_X / Δt = 70 / 10 = 7 m/s

                                                V_Y  = Δs_Y / Δt =  – 80  / 10 = – 8 m/s

6.        

7.       E              Diket : Δs = 100 – 40 = 60 cm

Δt = 40 – 0 = 40s

Dit : v_rata-rata = ..?

                                Dijwb : v_rata-rata  = Δs / Δt = 60 / 40 = 1,5 cm/s

v_rata-rata  = 0,015 m/s

hal 35

1.       Diket : v_o = 10 m/s

a = 2 m/s²

v_t = 0

Ditanya : t = ….? s = ….?

s = vo.t – ½ .a.t2 s = 10. 5 – ½. 2.52 s = 25 m

Dijawab : v_t = v_o – a.t

0 = 10 – 2.t

2.t = 10

t = 5 s

2.       Diket : h = 25 m

g = 10 m/s²

v_o = 0

vt = g.t vt = 10. √5 vt = 10 √5 m/s

Ditanya : t = ….? v_t = ….?

Dijawab : h = ½.g.t²

                   25 = ½.10.t²

                   t = √5 s

3.       Diket : v_o = 20 m/s

g = 10 m/s²

t = 1,5 s

vt = vo – g.t 0 = 20 – 10.t t = 2 s

hmaks = vo2 / 2.g hmaks = 202 / 2.10 hmaks = 20 m

Ditanya : v_t = ….? h_maks = ….? t =…?

Dijawab : v_t = v_o – g.t

                   v_t = 20 – 10.1,5

                   v_t = 5 m/s

1.       E.    108 km/jam = 108 .  = 30 m/s