Download Newton*s Second Law

Newton’s Second Law
Force = Mass x Acceleration
Torque
• In linear motion, the net force acting on an
object determines its acceleration. From this,
its position and velocity can be determined at
any particular time. Thus, the net force
completely determines the linear motion of
the object.
• However, in rotational motion, the same force
applied in different locations gives different
rotations!
• Thus, we need to use an expanded concept to
determine how an object will rotate.
• Torque is given by τ=r x F, where only the
components of r and F that are perpendicular
contribute to torque.
• Torque is a vector and is given in the unit of
N*m.
Finding the “Lever Arm”
• Torque is sometimes defined as the
product of the “lever arm” and the
applied force, where the lever arm is
the component of r that is
perpendicular to the force vector.
• To find the lever arm:
1. Extend a dotted line along the
same line as the force, the line of
action.
2. Draw a line from the center of
rotation to the line of action such
that your line is perpendicular to
the line of action. This line is the
lever arm.
Application
• A screwdriver is being used to pry the lid off a can of paint. A 1,000 N
force is exerted at the very end of the screwdriver, causing a 200 Nm
torque about an axis through the screwdriver's other end. The angle
between the force and the screwdriver's length is 53 degrees. What is
the length L of the screwdriver?
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T=rxF
T = rFsin(theta)
200 = L x (1000sin(53))
L = 200/798.635
L = .25m
Credits
Credits for the creation of this PowerPoint go to:
Alex Boone
Hunter Lavender
Christian Washington
Craig Jones II