bai 20: 1 Vat co khoi luong 2 kg chuyen dong thang nhanh dan deu tu trang thai nghi.Vat do di duoc 200cm trong thoi gian 2s.Tinh do lon hop luc tac dung vao vat
Bai 21: 1 luc khong doi tac dung vao 1 vat co khoi luong 5kg lam van toc cua no tang dan tu 2m/s den 8m/s trong 3s.Do lon cua luc tac dung vao vat la bao nhieu?