Hướng dẫn giải Bài 1 (Trang 92 SGK Vật lý 10, Bộ Chân trời sáng tạo)

Người ta tác dụng lực <span id="MathJax-Element-3-Frame" class="mjx-chtml MathJax_CHTML" style="margin: 0px; padding: 1px 0px; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: 400; font-size: 19.36px; letter-spacing: normal; overflow-wrap: normal; word-spacing: 0px; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; color: #000000; font-family: OpenSans, Tahoma, Helvetica, sans-serif; font-variant-ligatures: normal; font-variant-caps: normal; orphans: 2; widows: 2; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mi>F</mi><mo>&#x2192;</mo></mover></math>"><math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mi>F</mi><mo>→</mo></mover></math><math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mo></mo></mover></math> có độ lớn 80 N lên tay quay để xoay chiếc cối như Hình 14P.1. Cho rằng <span id="MathJax-Element-4-Frame" class="mjx-chtml MathJax_CHTML" style="margin: 0px; padding: 1px 0px; display: inline-table; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: 400; font-size: 19.36px; letter-spacing: normal; overflow-wrap: normal; word-spacing: 0px; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; color: #000000; font-family: OpenSans, Tahoma, Helvetica, sans-serif; font-variant-ligatures: normal; font-variant-caps: normal; orphans: 2; widows: 2; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mi>F</mi><mo>&#x2192;</mo></mover></math>"><math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mi>F</mi><mo>→</mo></mover></math><math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mo></mo></mover></math> có phương tiếp tuyến với bề mặt cối xay, khoảng cách từ tay quay đến tâm quay là d = 40 cm. Xác định moment của lực <span id="MathJax-Element-5-Frame" class="mjx-chtml MathJax_CHTML" style="margin: 0px; padding: 1px 0px; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: 400; font-size: 19.36px; letter-spacing: normal; overflow-wrap: normal; word-spacing: 0px; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; color: #000000; font-family: OpenSans, Tahoma, Helvetica, sans-serif; font-variant-ligatures: normal; font-variant-caps: normal; orphans: 2; widows: 2; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mi>F</mi><mo>&#x2192;</mo></mover></math>"><math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mi>F</mi><mo>→</mo></mover></math><math xmlns="http://www.w3.org/1998/Math/MathML"><mover><mo></mo></mover></math> đối với trục quay qua tâm cối xay. <img class="wscnph" style="max-width: 100%;" src="https://static.colearn.vn:8413/v1.0/upload/library/20062022/115_1-EVIfdT.png" /> Lời giải chi tiết: Ta có F = 80 N; d = 40 cm = 0,4 m => Moment lực đối với trục quay qua tâm cối xay là: M = F.d = 80.0,4 = 32 (N.m).