Mechanics - equations of motion, graphs, f = ma, work, energy and linear momentum Each section will open directly in a new window. Close each window as you finish. You might find it helpful to print this list of questions.
1 Kinematics and Motion Graphs
Read the Kinematics section and the Graphs section in the Mechanics index.
Essential questions
1 What are the units of velocity, and of acceleration?
2 In a single word, what does the slope of a position-time graph represent?
3 In a single word, what does the integral on a velocity-time graph represent?
4 How may each of these equatons be derived? Only a simple statement is required - do not show any working.
v = u + at
Acceleration due to gravity
Read the Acceleration due to gravity section in the mechanics index.
Essential questions
1 What exactly is the shape of the position-time graph when acceleration is constant?
2 What is the slope of the velocity-time graph when a ball (etc.) is in free fall clear of the floor?
3 What is the acceleration when the ball (etc. ) is at the top of its flight, and momentarily stationary?
4 Why is the measured acceleration of a large rubber ball (falling in the lab) a little less than 9.80 m/s/s?
2 Vectors and Equilibrium
Read the Vectors and Equilibrium sections in the mechanics index.
Essential questions
1 How are forces added when they are not in a straight line?
2 How is the difference in two vectors (forces) found?
3 What exactly do we mean when we say that three (or more) forces acting at a point are in equilibrium?
4 What two conditions are required for a rigid body to be in equilibrium?
5 What is the moment of a force?
6 Where is the weight of an extended body said to act?
3 Newton's Rules
Read the section on Newton's Rules in the mechanics index.
Essential questions [This is a large section. You need three main points.]
1 What is Newton's first rule in modern form?
a Explain why you know that a car traveling at constant speed on a level road has no unbalanced forces acting on it.
2 What is Newton's second rule in modern form?
a Give one example of f = ma in practice.
b How exactly did we verify the equation f = ma using a ball, a force probe, a motion detector, and a rubber band?
c Define inertia.
3 What is Newton's third rule?
a How did we verify the rule with two force probes and a rubber band?
4 Projectiles
Read the Projectiles section in the Mechanics index
Essential questions
1 What is the shape of the path of a projectile in the absence of air resistance?
2 What particular type of force gives this motion?
3 What can you say about the horizontal velocity for 'projectile' motion?
4 What is the equation of the trajectory (path) in vector form, neglecting air resistance?
5 How does the time of flight depend on the maximum height reached?
5 Friction and Skid distance
Read the sections on Friction and Skid distance in the Mechanics index.
Essential questions
1 What is the symbol for the coefficient of friction (k) in the equation F = k N ?
2 What is the definition of N and when is N equal to mg (in a simple situation)?
3 There are two coefficients of friction - what are they - and which one is larger?
4 How would you measure friction force in a way which avoids acceleration?
5 Why is skid distance D proportional to velocity squared in the case of a sliding block or car?
Sliding on an incline
Read the section Sliding on an incline in the Mechanics index.
Note:
a The reaction force (called the Normal force) is at right angles to a surface.
b The components of mg parallel and perpendicular to the plane.
c The formula m = tanq
6 Work and Kinetic Energy
Read the Work and Kinetic Energy section in the Mechanics index.
Essential questions
1 How is the simple definition of work as force x displacement modified when the force is not constant?
2 What unit is common to work and energy?
Note: Potential energy is another name for work done.
3 How is initial KE related to the incidental damage suffered by people in collisions?
4 What happens to kinetic energy in a collision?
5 Why is the total energy graph for a bouncing ball a series of steps?
7 Impulse, momentum and Collisions
Read the Impulse and momentum section and the Collisions section in the Mechanics index.
Essential questions
1 How is the definition of impulse modified if the force is not constant?
2 How is the change in a quantity defined - for instance the change in your salary from this week to the next?
3 What is meant exactly by "the conservation of momentum"?
4 Why is it important to get the signs of the velocities right in a momentum calculation before and after a collision?
Read the Golf balls section in the Mechanics index.
1 Define the coefficient of restitution?
8 Power
Read the Power section in the Mechanics index.
Essential questions
1 Who first defined the quantity we now call power, and why?
2 How is power related to 'work'?
3 What are the units of power?
4 How is the power available in a fluid flow related to the mass per second and the velocity of the flow?
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