1. Simple Machines Objectives: Levers Torque and Levers
Gears, Pulleys, and the Wheel-and-Axle

2. Gears: Transfer of Rotational Motion
T . N = t . n
T: Number of teeth on the driver gear
t: Number of teeth on the driven gear
N: Number of revolutions on the driver gear
n: Number of revolutions on the driven gear
Q5. A motor turning at 1250 rpm is fitted with a gear having 54 teeth. Find the speed of the driven gear if it has 45 teeth.

3. Torque Review Torque = (Force ) x (Lever Arm)
Q6. Which wrench requires you to apply less force in order to loosen a bolt. A long wrench or a short wrench?
(a) The long wrench
(b) The short wrench
(c) It doesn’t matter

4. Levers
(Effort Force)(Effort Arm) = (Resistance Force) (Resistance Arm)
Q7. (A first-class lever) A 10-lb objects is placed 1 ft to the left of fulcrum. How far from the fulcrum should a 5-lb force be applied to balance it.

5. Levers
(Effort Force)(Effort Arm) = (Resistance Force) (Resistance Arm)
Q8. (A first-class lever) A 10-lb objects is placed 1 ft to the left of fulcrum. How far from the fulcrum should a 5-lb force be applied to balance it.

6. Gears and Simple Machines20
P4. A wheel barrow 6.00 ft long is used to haul a 180-lb load. How far from the wheel is the load placed so that a person can lift it with a force of 45.0 lb?
6.0 ft
??? ft
180 lb
Pivot (Fulcrum)
Ans.

7. Gears and Simple Machines20
P5. A bar is used to raise a 1200-N stone. The pivot is placed 30.0 cm from the stone. The worker pushes 2.50 m from the pivot. What is the mechanical advantage? What force is exerted?
Ans.

8. Mechanical Advantage
(Effort Force)(Effort Arm) = (Resistance Force) (Resistance Arm) =
Effort Arm
Resistance Arm
Resistance Force
Effort Force
Resistance Force
Mechanical Advantage =
Effort Force

9. The Wheel-and-Axle
Q9. A wheel with radius 75.0 cm is attached to an axle of radius 13.6 cm. What force must be applied to the rim of the wheel to raise a 1000-N weight? =
Effort Arm
Resistance Arm
Resistance Force
Effort Force

10. Gears and Simple Machines20
P1. A driver gear with 60 teeth makes 1600 rpm. How many teeth must the driven gear have if it makes 480 rpm?
Ans.
P2. The larger of two gears in a clock has 36 teeth and turns at a rate of 0.50 rpm. How many teeth does the smaller gear have if it rotates at 1/30 rev/s?
Ans.
P3. An axle of radius 12.0 cm is used with a wheel of radius 62.0 cm. What force must be applied to the rim of the wheel to lift a weight of 975 N?
Ans.