Chapter 8 Flashcards
Who first described force as the impetus of motion?
Aristotle 384 BC
What did Galileo discover about force?
Force causes a change in velocity
Gravity pulls object to the ground
The effect of gravity is independent of the objects mass
Who developed the mathematical formulations for force, including gravity?
Newton - 1700’s
What are examples of forces that can be exerted without contact between objects?
Electromagnetism and gravity
What is the formal definition of force?
A push or pull exerted on one object by another object
Force always causes a change in motion - true or false
False
Which of the fundamental forces of the universe is the weakest?
Gravity
How can the theory of gravity be applied to Olympic weightlifting?
During a clean - because the effect of gravity is independent of mass - the athlete should focus more on getting under the bar quicker (beating gravity), rather than lifting the bar higher.
What condition is best described by Newton’s first law?
Equilibrium
Meaning there is no change in velocity and acceleration equals zero
What are Newton’s Laws of motion?
1 - An objects velocity will remain constant in the absence of unbalanced forces applied to the object
2 - When an unbalanced force is applied to an object, the velocity of the object will change (acceleration)
3 - Forces will always be equal and opposite. If object A exerts force onto object B, object B will exert an equal and opposite force onto object A.
What equation best describes Newton’s first law of motion?
Fa + Fb = 0
The sum of forces is equal to zero
What is the difference between equilibrium and static equilibrium?
Equilibrium means that the velocity is constant and the acceleration equals zero.
Static equilibrium is a special case of equilibrium wherein the velocity equals zero.
What principle describes the resistance to change in equilibrium?
Inertia
There are no forces acting on an object in equilibrium - true or false?
False - there can be forces, but the vector sum of the forces will be equal to zero.
Define dynamic equilibrium
When the vector sum of forces is equal to zero, but the velocity is not equal to zero, but remains constant (a=0)
A skydiver descends from the sky in a parachute at a constant velocity of -6.0m/s. Ignoring wind resistance, what vertical height would you have to land from to reach this velocity?
1.83 meters
What condition is described by Newton’s second law?
Dynamics
Define dynamics
In dynamics, change in velocity is not zero, therefore there is acceleration present. Since there is a net force applied to the object, impulse is applied, therefore, there will be a change in momentum.
In dynamics, the forces acting on the object are unbalanced. Algebraically, this can be stated as the vector sum of forces is not equal to zero.
Describe Newton’s second law in terms of the impulse-momentum relationship. What is the equation for impulse?
Impulse is the application of a force over time.
A change in momentum is a change in the velocity of mass (assuming the mass is constant).
Therefore when force is applied over a period of time, the velocity of an object with mass will change.
F=ma
A = v/t
F= mv/t
Ft = mv
Impulse = Ft
momentum = m*change in velocity
A goofball is designed to deform upon hitting. Why does this allow you to hit the ball farther?
Velocity is increased when the ball deforms upon hitting because of the impulse-momentum relationship.
Because the ball deforms, the amount of time that the force of the club is applied increases. This results in a greater impulse (Ft) and as a result, greater momentum (vm).
Usain Bolt has a low stride frequency compared to his competitors. How might this be beneficial for his performance?
Use Newton’s second law to describe.
Usain Bolt has a relatively low stride frequency,
which means that the time per stride is relatively long. This could translate to a
longer stance time. The benefit of having a longer stance time (within reason) is that
force can be exerted against the ground for a longer time, resulting in greater
impulse. The greater impulse would result in greater changes in momentum and
velocity during flight.
According to Newtons 3rd law, reaction forces must be … ?
Equal in magnitude, opposite in sense, and co-linear.
The external cue “push into the ground” can help to maximize _________ during a vertical jump.
Ground reaction forces.
