Tóm tắt: F= 200N, s=10m

t=5s, alpha=60° ,A=?, P=?

Công của lực kéo là:

A=F× s× cos alpha= 200× 10 × cos 60° =1000 (J) 

Công suất của người đó là: P=A/t =1000/5 =200(W)

Khối lượng của vật: 0.75kg

Vận tốc của vật: 6.32m/s

Tóm tắt: m= 200kg, h=10m, g=10m/s2, F1=1500N, s=2s=20m

Công có ích: A ích= Wd=mgh= 200×10×10=20000(J)

Công toàn phần: A toàn phần=F1×s=1500×20=30000(J)

Hiệu suất của hệ thống là: H=A ích/ A toàn phần ×100%= 20000/30000×100%=66.6 %

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