Tham khảo tài liệu 'science of everyday things vol. 2 - physics episode 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | A SEESAW ROTATES ON AND OFF THE GROUND DUE TO TORQUE IMBALANCE. Photograph by Dean Conger Corbis. Reproduced by permission. TORQUE case there is also a place where force is being applied. On the seesaw it is the seats each holding a child of differing weight. In the realm of physics weight is actually a variety of force. Whereas force is equal to mass multiplied by acceleration weight is equal to mass multiplied by the acceleration due to gravity. The latter is equal to 32 ft m sec2. This means that for every second that an object experiencing gravitational force continues to fall its velocity increases at the rate of 32 ft or m per second. Thus the formula for weight is essentially the same as that for force with a more specific variety of acceleration substituted for the generalized term in the equation for force. As for moment arm this is the distance from the pivot point to the vector on which force is being applied. Moment arm is always perpendicular to the direction of force. Consider a wrench operating on a lug nut. The nut as noted earlier is the pivot point and the moment arm is the distance from the lug nut to the place where the person operating the wrench has applied force. The torque that the lug nut experiences is the product of moment arm multiplied by force. In English units torque is measured in pound-feet whereas the metric unit is Newtonmeters or N m. One newton is the amount of force that when applied to 1 kg of mass will give it an acceleration of 1 m sec2 . Hence if a person were to a grip a wrench 9 in 23 cm from the pivot point the moment arm would be ft m. If the person then applied 50 lb N of force the lug nut would be experiencing pound-feet N m of torque. The greater the amount of torque the greater the tendency of the object to be put into rotation. In the case of a seesaw its overall design in particular the fact that it sits on the ground means that its board can never undergo anything close to 360 .
