# Physics for Life Sciences

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1. Prefixes tera to pico
• tera T 1012
• giga G 109
• mega M 106
• kilo k 103
• hecto h 102
• deka d 101
• deci d 10-1
• centi c 10-2
• milli m 10-3
• micro μ 10-6
• nano n 10-9
• pico p 10-12
2. What is meant by significant figures
• The figures of a number that express a magnitude to a specified degree of accuracy, rounding up or down the final figure.
• 3.14159 to four significant figures is 3.142
3. Know the SI units
• Length m metre
• Times s second
• Mass kg kilogram
4. Unit Conversion
• 1 cm = 0.3937 inches
• 1 m = 39.37 inches
• 1 km = 0.6214 miles
• 1 L = 1,000 ml = 1,000 cm3
• 1 km/hr = 0.278 m/s = 0.621 miles/hr
• 1 m/s = 3.6 km/hr = 2.237 miles/hr
• 1 rev/min (rpm) = 0.1047 rad/s
• 1 W = 1J/s
• 1 Pa = 1 N/m2
• 1 day = 8.64 x 104 sec
5. Pythagoras, SOCAHTOA
The theorem that in a right angled triangle, the square of the length of the hypotenuse equals the sum of the squares of the other two sides

• sin = opposite/hypo
• cos = adjacent / hypo
6. Displacement
Velocity
Acceleration
The displacement of an object is the change in position of the object

Velocity: a measure of the rate of motion of a body expressed as the rate of change of its position in a particular direction with time, m/s

Acceleration: the rate of increase of speed or the rate of change of velocity, a
7. Average vs instantaneous velocity & acceleration
• An object's average velocity over a particular time interval, Δt, is its
• displacement Δx during that time interval, divided by Δt

The instantaneous velocity is the average velocity taken over an infinitesimally short time interval

An object's average acceleration over a time interval Δt is Δv/Δt

Instantaneous acceleration is the average acceleration taken over an infinitesimally short time interval
8. Kinematics equations
• v = vo + at
• x = xo + vot + ½at2
• v2=vo2 +2a(x-xo)
• average v=(v + vo)/2
9. Newton's Laws of Motion
Every object continues in its state of rest or of uniform velocity in a straight line as long as no net force acts on it

The acceleration of an object is directly proportional to the net force acting on it and is inversely proportional to its mass. The direction of the acceleration is in the direction of the net force acting on the object. ΣF=ma

Whenever one object exerts a force on a second object, the second exerts an equal force in the opposite direction on the first
10. Weight
Normal force
friction
tension
Elastic force
The magnitude of the force of gravity on an object is commonly called the object's weight

When a contact force acts perpendicular to the common surface of contact, it is referred to as the normal force

• When two objects slide over one another, the force of friction that each object exerts on the other can be written approximately as Ffr = μKFN, where FN is the normal force and μK is the coefficient of kinetic friction.
• If the objects are at rest relative to each other, then Ffr is just large enough to hold them at rest and satisfies the inequality FfrsFN, where μs is the coefficient of static friction
• When a flexible cord pulls on an object, the cord is said to be under tension, and the force it exerts on the object is the tension FT

• The normal force is an elastic force caused by the deformation of the surface
• Tension force: another elastic force caused by the stretching of the rope, rod, or spring or whatever it is
11. Problem solving