Torque. It is easier to open a door when a force is applied at the knob as opposed to a position closer to the hinges. The farther away the force, the more torque there is. Torque – the force(s) that cause an object to rotate
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It is easier to open a door when a force is applied at the knob as opposed to a position closer to the hinges.
The farther away the force, the more torque there is.
Torque is the product of the force and the perpendicular distance from the axis of location
The force is extended to meet the moment arm which is drawn perpendicular to force through the hinge.
τ = rsinθF
The force is resolved into components and the perpendicular component is used with the original moment arm.
τ = rFsinθ
Either method for calculating torque is acceptable
τ = torque (mN)
r =moment arm (m)
F = force (N)
The force and the moment arm should always be perpendicular to each other.
“Static” problems are ones where the objects in question are stationary.
Is there a net force acting on the traffic light?
No…the light is stationary.
ΣFx = 0 and ΣFy = 0
Is there a net force?
Will it move?
It rotates because of the torge
Στ ≠ 0
At what distance must child B (m = 25 kg) sit in order to balance the seesaw?
What is the normal force acting on the seesaw by the fulcrum?
The string is exerting a force on the object
Net force? Acceleration?
Yes, even though the speed is constant.
The direction is changing; therefore, the velocity is changing.
It is accelerating
The planets have a radial or tangential speed around the orbit.
The force that is causing the motion is directed toward the center.
aR = radial (centripetal) acceleration (m/s2)
v = radial speed (m/s)
r = radius of circle (m)
A centripetal force is not a new type of force. Many of the forces we have discussed are centripetal forces when they cause objects to move in circles.
Σ FR = net centripetal force (N)
m = mass (kg)
aR = centripetal acceleration (m/s2)
What would be the tension of the cord at the bottom if the ball is traveling twice the speed of the 1st part?
What if the pavement was covered with ice (μs = 0.25)?
Banked turns assist in helping cars navigate turns when there is not sufficient friction for excessive speeds. How much of an angle is needed so that friction is unnecessary?
How much of a banked turn would be needed for a 1000-kg car to steer through a 50-m radius turn at a speed of 14 m/s?
The mass is irrelevant. Why?
Newton wondered why if an apple falls out of a tree toward the Earth why the moon doesn’t fall toward the Earth also.
Newton theorized that the Moon did not get attracted with the same force as the apple nor did it fall with the same gravitational acceleration. Why not?
1. The moon was much farther away from the Earth than an apple on the surface.
2. The moon was much larger than the apple.
G = gravitational constant = 6.67 x 10-11 Nm2/kg2
m1 = mass #1 (kg)
m2 = mass #2 (kg)
r = distance between centers of mass (m)
Newton’s Law of Universal Gravitation applies between any two objects that have mass regardless of size.
Fg = Gm1m2/r2
mg = GmEm/rE2
g = GmE/rE2
g = gravitational acceleration (m/s2)
mE = mass of Earth (kg)
r = radius of Earth (m)
Satellites are objects that orbit the Earth. They are given a radial speed that counteracts the effects of gravity so that they maintain either a circular path.
Different from real weightlessness because the satellite and occupants are actually falling, but the radial speed keeps them in orbit.
It is like the apparent weightlessness of an elevator moving down.
Plane makes large parabolic turns with 30-s intervals of weighlessness.
What do they experience at the bottom of the curve?