## Pulley

1. There are 2 types of pulley, the fixed pulley and the movable pulley.

 (“Fixed pulley” by César Rincón available under a Creative Commons Attribution-Share Alike 3.0 Unported)
 (“Movable pulley” by Johjak available under a Creative Commons Attribution-Share Alike 3.0 Unported)
1. In SPM, we will only discuss the fixed pulley.
2. The fixed pulley change the direction, without changing the magnitude of the force.
3. In SPM, we assume all pulleys are smooth (no friction) unless it is stated otherwise.

## Apparent Weight of an Object in a Lift

1. When a man standing inside an elevator, there are two forces acting on him.
1. His weight, (W) which acting downward.
2. Normal reaction (R), acting in the opposite direction of weight.
2. The reading of the balance is equal to the normal reaction (R).
3. Figure below shows the formula to calculate the reading of the balance at different situation.

Example 1:
Subra is standing on a balance inside an elevator. If Subra’s mass is 63kg, find the reading of the balance when the lift,

1. stationary
2. moving upward with a constant velocity, 15 ms-1.,
3. moving upward with a constant acceleration, 1 ms-2.
4. moving downward with a constant acceleration, 2 ms-2.

a.

W = mg
W = (63)(10) = 630N

b.

W = mg
W = (63)(10) = 630N

c.

R = mg+ma
R = (63)(10)+(63)(1)
R = 693N

d.

R = mg−ma
R = (63)(10)−(63)(2)
R = 504N

Example 2:
A 54kg boy is standing in an elevator. Find the force on the boy’s feet when the elevator

1. stands still
2. moves downward at a constant velocity of 3 m/s
3. decelerates downward with at 4.0 m/s2,
4. decelerates upward withat 2.0 m/s2.

a.

W = mg
W = (54)(10) = 540N

b.

W = mg
W = (54)(10) = 540N

c.

R=mg+ma
R=(54)(10)+(54)(4)
R=756N

d.

R=mg−ma
R=(54)(10)−(54)(2)
R=432N

## Linear Motion

1. Kinematics is the research regarding the types of movement of an object without referring to the forces that cause the movement of the object.
2. Movement along a straight line is called linear motion.
3. Under the linear motion, we study the
1. distance and displacement
2. speed and velocity
3. acceleration
and the relationship between them.