Physics Revision

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Questions and Answers

What does the term 'significant figures' indicate in a measured quantity?

The level of precision of the quantity (correct)

The scientific notation of the quantity

The units of measurement used

The number of digits in the quantity

If a calculation involves numbers with different significant figures, how should the final answer be rounded?

To the average number of significant figures used

To the highest number of significant figures used

Not rounded at all

To the least number of significant figures used (correct)

Which of these represents two significant figures?

9.80 (correct)

0.0055

0.020

1204

When rounding a result from a multiplication or division calculation, to what should the result be rounded?

The same number of significant figures as the least precise number used Signup and view all the answers

In the expression 10.1 + 12.367 + 0.459, how should the final answer be reported?

21.9 Signup and view all the answers

What is the implicit uncertainty when a physical quantity is reported as 9.8 ms−1?

±0.05 ms−1 Signup and view all the answers

What condition must be satisfied for a system to be in static equilibrium?

The net force and torque on the system must both be zero. Signup and view all the answers

Which factor contributes to a system being in stable equilibrium?

The system returns to equilibrium after a small displacement. Signup and view all the answers

In which condition will an object tend to topple over?

When the center of mass is outside the area spanned by the feet. Signup and view all the answers

What happens to the torques acting on the feet when an individual stands perfectly balanced on tiptoe?

The torques balance each other out. Signup and view all the answers

Which statement about torques is true when the center of mass is shifted to the left of the foot area during standing?

Both torques will be negative. Signup and view all the answers

What primarily defines the term 'torque' in mechanics?

The distance from the pivot point multiplied by the force applied. Signup and view all the answers

What property of the cable is assumed when it is described as massless?

Its mass is negligible compared to the body's mass. Signup and view all the answers

Which of the following statements about static and kinetic friction is true?

Static friction acts when there is no relative motion. Signup and view all the answers

According to Newton's second law, what is the correct expression for the relationship between force, mass, and acceleration?

$F = ma$ Signup and view all the answers

What is the direction of the frictional force when an object is about to slide over a surface?

Opposite to the direction of intended motion Signup and view all the answers

Which of the following correctly describes the normal force?

It is a component of the contact force that is perpendicular to the surfaces in contact. Signup and view all the answers

What characterizes the tension force in a cable?

It pulls on both bodies with the same force magnitude. Signup and view all the answers

Why is the coefficient of kinetic friction always smaller than the coefficient of static friction?

Objects are not locked in place during kinetic friction. Signup and view all the answers

What does Newton's third law state regarding forces?

For every force that is applied, there is an equal and opposite force applied by the other object. Signup and view all the answers

What is the primary focus of the study of statics in biomechanics?

Examining bodies that are not accelerating Signup and view all the answers

Which statement accurately describes a system in dynamic equilibrium?

The system is in equilibrium while moving at constant velocity. Signup and view all the answers

How can each force acting on a body in static equilibrium be expressed?

Resolved into components in three dimensions Signup and view all the answers

Which of the following best defines torque in a static context?

A measure of the tendency of a force to rotate an object Signup and view all the answers

What is necessary for an object to be in static equilibrium?

The sum of forces in all directions must equal zero Signup and view all the answers

What is meant by the center of gravity of a body?

The point at which the mass of the body is concentrated Signup and view all the answers

In which scenario would the principle of moments be applicable?

When analyzing forces on a lever in equilibrium Signup and view all the answers

Which condition is NOT associated with static equilibrium?

There is continuous motion occurring Signup and view all the answers

Which of the following correctly states the conditions for equilibrium in all three dimensions?

The sum of the forces in each direction must be zero Signup and view all the answers

Which of the following examples is specifically associated with investigating statics in the body?

Examining forces acting on the lower arm while lifting a weight Signup and view all the answers

What is the formula to calculate work done by a constant force at an angle?

W = F d cos θ Signup and view all the answers

Which statement correctly describes work as a physical quantity?

Work can be both positive and negative. Signup and view all the answers

When a falling object gains kinetic energy, what is happening to its potential energy?

It decreases as the object falls. Signup and view all the answers

In which scenario is the work done on an object zero?

When there is no displacement. Signup and view all the answers

What primarily characterizes mechanical efficiency in work and energy systems?

The ratio of useful energy output to total energy input. Signup and view all the answers

When is work done by a force considered positive?

When the force has a vector component in the same direction as the displacement. Signup and view all the answers

What is the unit of work in SI units?

Joule (J) Signup and view all the answers

What happens to the work done when the angle between force and displacement is 90 degrees?

Work equals zero. Signup and view all the answers

Which of the following statements about kinetic energy is true?

Kinetic energy can be measured in joules. Signup and view all the answers

Which of the following explains potential energy?

Energy stored in an object as a result of its position or configuration. Signup and view all the answers

What is the SI unit of power?

Watt Signup and view all the answers

How is average power calculated using work and time?

Power = Work / Time Signup and view all the answers

In the provided example, what is the work done by the man to raise his center of gravity?

2060 J Signup and view all the answers

What is the average power produced by the man running up the stairs?

1030 W Signup and view all the answers

Which formula represents the relationship between power, force, and distance over time?

P = F × v Signup and view all the answers

Study Notes

Significant Figures

Significant figures are a conventional method in science to represent precision.
More significant figures imply higher precision.
The number of significant figures usually equals the number of digits provided.
For example, 9.8 ms−2 has two, while 9.81 ms−2 has three significant figures.

Uncertainty in Measurements

When a quantity is stated with two significant figures, the final digit has an implicit uncertainty of ±0.05.
In calculations, results should maintain the same level of precision as the least precise input.
Rounding should be performed on the final answer, not intermediate steps.

Rules for Significant Figures in Calculations

When multiplying or dividing, the final answer should have the same number of significant figures as the least precise input.
When adding or subtracting, the final answer should have the same number of decimal places as the input with the least number of decimal places.

Tension

Tension refers to the stretching force within a cable or cord.
It is assumed that the cable is massless and unstretchable.
The cable exerts an equal force on both bodies it connects.

Friction

Friction opposes relative motion between two surfaces in contact.
Static Friction: Resists a potential motion.
Kinetic Friction: Resists a moving object.
The coefficient of friction is calculated from the equation f = μN.
The coefficient of static friction is always greater than the coefficient of kinetic friction.

Newton's Laws of Motion

First Law: An object remains at rest or at constant velocity unless acted upon by a net force.
Second Law: Force is equal to mass times acceleration (F = ma).
Third Law: For every action, there is an equal and opposite reaction.

Forces in the Human Body

Normal Force (N): The perpendicular contact force between two objects.
Tension Force (T): A force that stretches intermolecular bonds.
Friction Force (f): A force that resists relative motion between surfaces.

Statics

Statics is the study of bodies in equilibrium, meaning they are not accelerating.
Dynamic equilibrium occurs when a system is in motion at constant velocity or rotating at a constant rate.
Static equilibrium occurs when the system is at rest.
A system is in equilibrium when the net force and net torque are zero.

Stability

Stability is essential for standing and all types of motion.
Overall stability requires the center of mass to be over the area spanned by the feet for a rigid mass.
If the center of mass is outside the support base area, instability occurs, and the body may topple over.
The body is most stable when the line of gravity is near the center of the support base.

Torque

Torque is the tendency of a force to rotate an object around an axis, fulcrum, or pivot point.

Levers in the Body

First Class Lever: The fulcrum is between the effort (muscle force) and the load (weight). Example: Head movement.
Second Class Lever: The load is between the effort and the fulcrum. Example: Standing on tiptoes, a less common lever in the body.
Third Class Lever: The effort is between the load and the fulcrum (most common lever). Example: Biceps brachii balancing lower arm against a weight.

Lower Arm Example in Statics

The biceps brachii muscle contracts to balance the weight of the object held in the hand, preventing rotation of the lower arm about the elbow joint.
The elbow joint functions as a hinge.

Work

Work is the process of transferring energy from one form to another, influenced by the type of process
Measured in Joules (J)
Work done by a constant force is the product of displacement and the force component parallel to the displacement
W = F// × d = F d cos q
Work is a scalar quantity, only having magnitude, which can be positive or negative
Positive work is done when the force and displacement are in the same direction.
Negative work is done when the force and displacement are in opposite directions.
Zero work is done when the force and displacement are perpendicular or if there is no displacement.

Kinetic Energy

The energy of an object in motion
Kinetic Energy = 1/2 * mv^2 where m is mass and v is velocity
Measured in Joules (J)

Potential Energy

Energy stored by an object due to its position or configuration
Types of potential energy include gravitational potential energy and elastic potential energy
Gravitational potential energy is determined by an objects mass, the acceleration due to gravity, and its height above a reference point
It is measured in Joules (J)

Power

The rate at which work is done
Power = Work / Time
Power is measured in Watts (W)
1 Watt (W) = 1 Joule (J) per second (s)
Power = Force x Velocity

Mechanical Efficiency

The ratio of output work to input work
A perfect machine converts all input energy into output work
Real machines always lose some energy to dissipative forces which result in heat, sound, or other forms of energy not contributing to the desired work
Mechanical Efficiency = Work Output / Work Input
Expressed as a percentage or decimal

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Description

This quiz covers the concepts of significant figures and how they relate to measurement precision in science. It explores rules for calculations involving significant figures and the implications of uncertainty in measurements. Test your understanding of these essential principles in scientific calculations.