\(72\left(\dfrac{km}{h}\right)=20\left(\dfrac{m}{s}\right)\)

Câu 1.

\(t=\dfrac{v}{g}=\dfrac{10}{10}=1s\)

\(S=\dfrac{1}{2}gt^2=\dfrac{1}{2}\cdot10\cdot1^2=5m\)

Câu 2.

\(S=\dfrac{1}{2}gt^2\)\(\Rightarrow t=\sqrt{\dfrac{2S}{g}}=\sqrt{\dfrac{2\cdot25}{10}}=2s\)

\(v=g\cdot t=10\cdot2=20\)m/s

Chọn C

Ta có 1m/s=3,6k/h

➜a) 5m/s = 18 km/h b) 72km/h = 20 m/s

b) 15m/s = 5 km/h d) 36 km/h = 10m/s

Giải a)

\(5\left(\frac{m}{s}\right)=18\left(\frac{km}{h}\right)\\ 72\left(\frac{km}{h}\right)=20\left(\frac{m}{s}\right)\)

b)

\(15\left(\frac{m}{s}\right)=54\left(\frac{km}{h}\right)\\ 36\left(\frac{km}{h}\right)=10\left(\frac{m}{s}\right)\)

ta có \(1m/s=\frac{1}{1000}.3600=3,6km/h\)

\(1km/h=\frac{1000}{3600}=\frac{5}{18}m/s\)

a) 5m/s = 18km/h

b) 72km/h = 20m/s

c) 15m/s = 54km/h

d) 36km/h = 10m/s

Ta có :

a ) 5m/s = 1/200 km/ 1/3600 h = 18 km/h

b ) 15m/s = 3/200 km/ 1/3600 h = 54 km/h

c ) 72km/h = 72000 m/ 3600 s = 20 m/s

d ) 450m/phút = 9/20 km/ 1/60 h = 27 km/h

= 450m/ 60 s = 7,5 m/s

C

C

\(1km\)/\(h=\dfrac{1}{3,6}m\)/\(s\)

\(54km\)/\(h=\dfrac{54}{3,6}=15m\)/\(s\)

\(\Rightarrow ChọnC\)

Đáp án A

Mình nghĩ là

C 20m/s

72 km/h = (72*1000:3600) m/s = 20m/s.

Chọn C

A)

B) 20m/s =……72……km/h

72km/h=………20……m/s

35m/s=………126………km/h

216km/h=………60……m/s