Displacement, Position, Velocity, Acceleration, and Force
What does the slope of the tangent to the curve on a velocity-time graph measure?
What quantity is represented by the area under a velocity-time graph?
The change in displacement.
If you were given initial and final velocities and the constant acceleration of an object, and you were asked to find the displacement, what equation would you use?
vf2 = vi2 + 2ad
Would a ball that is dropped by an astronaut hit the surface of the moon with a greater, equal, or lesser speed than that of a ball dropped from the same height to Earth?
The ball will hit the moon with a lesser speed because the acceleration due to gravity is less on the moon.
The planet Jupiter has about three times the gravitational acceleration of Earth. Suppose a ball is thrown vertically upward with the same initial velocity on Earth and on Jupiter. Neglect the effects of Jupiter's atmosphere resistance and assume that gravity is the only force on the ball. (a) How does the maximum height reached by the ball on Jupiter compare to the maximum height on Earth? (b) If the ball on Jupiter were thrown with an initial velocity that is three times greater, how would this affect your answer to part a?
a) A ball on Jupiter would rise to a height of one-third that on Earth.
b) Now, the ball on Jupiter will rise to three times that on earth.
Suppose that the acceleration of an object is zero. Does this mean that there are no forces acting on it?
No, it just means there is constant force because the object could be moving at a constant speed or be stationary.
Gravity and Weight
The push of a hand, thrust, tension, friction, air drag, spring force
Not a force
acceleration, mass x acceleration, inertia, mass
You take a ride in a fast elevator to the top of a tall building and ride back down while standing on a bathroom scale. During which parts of the ride will your apparent and real weights be the same?
a) continuing upwards at constant velocity
b) continuing downwards at constant velocity
During which parts will your apparent weight be less than your real weight in the elevator?
a) During which parts will your apparent weight be less than your real weight?
b) speeding up while moving downwards
During which parts will your apparent weight be more than your real weight in an elevator?
a) accelerating upwards
b) slowing while moving downwards
Can the co-efficient of friction ever have a value such that a skier would be able to slide uphill at a constant velocity?
No, friction is a reaction force to the gravity force down. By Newton's Third Law, the greatest possible friction can only equal down force, never exceed.
You are sitting at a baseball game when a foul ball comes in your direction. You prepare to catch it barehanded. To catch it safely, should you move your hands toward the ball, hold them still, or move them in the same direction as the moving ball?
You should move them in the same direction the ball is moving.
Two bullets of equal mass are shot at equal speeds at blocks of wood on a smooth ice rink. One bullet, made of rubber, bounces off the wood. The other bullet, made of aluminum, burrows into the wood. In which case does the block of wood move faster?
The rubber bullet causes the block to move faster.
Can a bullet have the same momentum as a truck?
A pitcher throws a curve ball to the catcher. Assume that the speed of the ball doesn't change in flight.
The pitcher and catcher exert the same impulse on the ball. The catcher exerts the larger force on the ball.
The movement of an object at a constant speed around a circle with a fixed radius
Uniform Circular Motion
Gravity is considered this type of force
If an object is not moving or moving at constant velocity then the net force on the object is
The force on box A from box B is equal to the force of box B on box A is an example of what law
Newton's third law
Newton's First Law
An object at rest will remain a rest, and a moving object will continue moving in a straight line with constant speed, if and only if the net force is 0
Newton's Second Law
Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object). (mass x acceleration)
Newton's Third Law
For every action there is an equal and opposite re-action.
Mechanical energy is not conserved when this is present
If no external forces act on a system then this is conserved?
This collision has no loss of kinetic energy
When considering a change in momentum what two variables must you consider?
Force and Time
On a velocity-time graph a flat line indicates
An object that slows down in the positive direction exhibits
A girl accelerates down a slide with a coefficient of friction equal to 0.10. What forces are responsible for her acceleration?
gravity and friction
Explain why an aluminum ball and a steel ball of similar size and shape, dropped from the same height, reach the ground at the same time.
Size can effect the speed of the drop because air resistance will slow the object. But two objects that are of the same size will have the same air resistance therefore fall at the same speed regardless of their weight.
Can you go around a curve with constant acceleration?
No you cant go around the curve with zero acceleration because when going around a curve you are changing direction.