Physics 1 Final Concepts
Two unequal masses M and m (M > m) are connected by a light cord passing over a pulley of negligible mass, as shown in the figure. When released, the system
accelerates.
When a rigid body rotates about a fixed axis,
all the points in the body have the same angular acceleration.
When two objects slide by one another, the force of friction between them is
always equal to μkn.
A mass M is attached to an ideal massless spring. When this system is set in motion, it has a period T. The period if the mass is doubled to 2M is
√(2)M.
A certain frictionless simple pendulum having a length L and mass M swings with period T. If both L and M are doubled, the new period is
√(2)T.
A certain planet has an escape speed V. If another planet of the same size has twice the mass as the first planet, its escape speed will be
√(2)V.
In a collision between two objects having unequal masses, the magnitude of the impulse imparted to the lighter object by the heavier one compare with the magnitude of the impulse imparted to the heavier object by the light one is that both objects receive the same
impulse.
An object is executing simple harmonic motion, the acceleration is zero when the speed of the object is a maximum, the acceleration is a maximum when the displacement of the object is a maximum, and the acceleration is a maximum when the object is
instantaneously at rest.
Tension increases if
the angle increases, and if the object increases in weight.
When an object is suspended at rest from two non-vertical ropes, there three forces acting on it:
(1) a tension in the left rope, (2) a tension in the right rope, and (3) the object's weight. The resultant of rope tensions must have the same magnitude as the object's weight.
Two objects have the same size and shape, but one is much heavier than the other. When they are dropped, simultaneously from a tower,
they reach the ground at the same time, but the heavier one has a greater momentum.
Frequency =
1/T
If the mass of the earth and all objects on it were suddenly doubled, but the size remained the same, the acceleration due to gravity at the surface would become
2 times what it now is.
A satellite in a circular orbit of radius R around planet X has an orbital period T. If Planet X had one-fourth as much mass, the orbital period of this satellite in an orbit of the same radius would be
2T.
What is an example of an inertial frame of reference?
A sky diver falling at terminal velocity.
What is Newton's Law of Inertia?
Every object in a state of uniform tend to remain in that state of motion unless an external force is applied to it.
A restoring force of magnitude F acts on a system with a displacement of magnitude x. The case that will the system undergo simple harmonic motion, is
F ∝ x.
What is Newton's law of action-reaction?
For every action there is an equal and opposite reaction.
An object is moving to the right and experiencing a net force that is directed to the right. What is the happens to the magnitude of force and the speed of the object?
The magnitude of the force is decreasing with time. The speed of the object is increasing.
An object is moving to the right, and experiencing a net force that is directed to the right. What happens with the magnitude of force and the speed?
The magnitude of the force is decreasing with time. The speed of the object is increasing.
An object is moving to the right in a straight line. The net force acting on the object is also directed to the right, but the magnitude of the force is decreasing with time. What is the objects movement?
The object will continue to move to the right, with its speed increasing with time.
What is Newton's second law of motion?
The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.
Two bullets are fired simultaneously parallel to a horizontal plane. The bullets have different initial velocities. Who strikes the plane first?
They strike the horizontal plane at the same time.
A certain planet has an escape speed V. If another planet has twice the mass and radius as the first planet, its escape speed will be
V.
A ball is thrown upwards and returns to the same position. Compared with its original speed after release, its speed when it returns is
about the same.
If we double only the amplitude of a vibrating ideal mass-spring system, the mechanical energy of the system, it increases
by a factor of 4.
Only when there is no force at all, or when two or more forces combine to zero,
can an object be in equilibrium.
A small glider is coasting horizontally when suddenly a very heavy piece of cargo falls out of the bottom of the plane. You can neglect air resistance. Just after the cargo has fallen out neither the cargo nor the plane
change speed.
Angular momentum and the total mechanical energy about the center of the planet is
conserved.
Disregarding air resistance, objects fall with
constant acceleration.
A massive block is being pulled along a horizontal frictionless surface by a constant horizontal force. The block must be moving with a
constant nonzero acceleration.
When a parachutist jumps from an airplane, he eventually reaches a constant speed, called the terminal speed. Once he has reached terminal speed the force of air drag on him is equal to
his weight.
Two cars of equal mass collide inelastically and stick together after the collision. Before the collision, their speeds are v1 and v2. The speed of the two-car system after the collision depends on the
directions in which the cars were moving before the collision.
A satellite is orbiting the earth. If a payload of material is added until it doubles the satellite's mass, the earth's pull of gravity on this satellite will
double but the satellite's orbit will not be affected.
According to Newton's 3rd Law, the force on the (smaller) moon due to the (larger) earth is
equal in magnitude but antiparallel to the force on the earth due to the moon.
If the kinetic energy of the block is increasing, the block must be moving toward
equilibrium.
The reason an astronaut in an earth satellite feels weightless is that the astronaut is
falling.
If the period of oscillations is doubles, the frequency is
halved.
When the horizontal motion is independent of the vertical motion, the projectile motion
has no air drag.
Two objects of the same size, but unequal weights are dropped from a tall tower. Taking air resistance into consideration, the object to hit the ground first will be the
heavier object.
Two identical stones are dropped from a tall building, one after the other. Assume air resistance is negligible. While both stones are falling, the vertical distance between them will
increase.
A person in a car is driving down a straight road. The instantaneous acceleration is decreasing with time, but is directed in the direction of the cart's motion. The speed of the car is
increasing with time.
When the average velocity of an object has a constant velocity, it is always equal to its
instantaneous velocity.
A metal bar is hanging from a hook in the ceiling when it is suddenly struck by a ball that is moving horizontally. The ball is covered with glue, so it sticks to the bar. During this collision, the angular momentum of the system (ball and bar)
is conserved about the hook because neither the hook nor gravity exerts any torque on this system about the hook.
A stone is thrown vertically upwards, reaches a highest point, and returns to the ground. When the stone is at the top of its path, its acceleration
is directed downwards.
For general projectile motion, when the projectile is at the highest point of its trajectory its velocity
is perpendicular to the acceleration.
In a graph of uniform motion,
it is a straight line, the slope is constant
A ball is released from rest on a no-slip surface, as shown in the figure. After reaching its lowest point, the ball begins to rise again, this time on a frictionless surface as shown in the figure. When the ball reaches its maximum height on the frictionless surface
it is at a lesser height as when it was released.
A shell that is initially at rest explodes into two fragments, one fragment 25 times heavier than the other. If any gas from the explosion has negligible mass, then the
kinetic energy change of the lighter fragment is 25 times as great as the kinetic energy change of the heavier fragment, and the momentum change of the lighter fragment is exactly the same as the momentum change of the heavier fragment.
Consider a uniform solid sphere of radius R and mass M rolling without slipping. Its transitional kinetic energy is
larger than its rotational kinetic energy.
Two bodies P and Q on a smooth horizontal surface are connected by a light cord. The mass of P is greater than that of Q. A horizontal force F (of magnitude F) is applied to Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P will be
less than F but not zero.
Two objects having masses m1 and m2 are connected to each other as shown in the figure and are released from the rest. There is no friction on the table surface or in the pulley. The masses of the pulley and the string connecting the objects are completely negligible. The tension T in the string just after the objects are release is
less than m2*g.
Whenever the net force on an object is zero, the object is said to be in
mechanical equilibrium.
Two planets having equal masses are in circular orbit around a star. Planet A has a smaller orbital radius than planet B. Planet A has
more kinetic energy, less potential energy, and less mechanical energy (potential plus kinetic) than planet B.
Two cars collide inelastically and stick together after the collision. Before the collision, the magnitudes of their momenta are p1 and p2. After the collision, the magnitude of their combined momentum depends on
the directions in which the cars were moving before the collision.
Assume that a pitcher throws a baseball so that it travels in a straight line parallel to the ground. The batter then hits the ball so it goes directly back to the pitcher along the same straight line. The impulse on the ball caused by the bat will be in the
negative x-direction
An object under the influence of only one force can
not be in equilibrium.
For an object at rest on a horizontal surface, the support force must equal the
object's weight.
When two objects are in contact with no relative motion, the frictional force is determined by
other forces acting on the objects so it can be either equal to or less than μsn.
Two cars collide inelastically and stick together after the collision. Before the collision, their momenta are p1 and p2. After the collision, their combined momentum is
p, which is equal to p1 + p2.
A stock person at the local grocery store has a job consisting of the positive work on the boxes when
picking up boxes of tomatoes from the stockroom floor and accelerating to a comfortable speed.
Two objects are dropped from a bridge, an interval of 1.0 s apart, and experience no appreciable air resistance, as time progresses, the difference in their speeds
remains constant.
When a board with a box on it is slowly tilted to larger and larger angle, common experience shows that the box will at some point "break loose" and start to accelerate down the board. The box begins to slide once the component of gravity acting parallel to the board Fg just begins to exceeds the maximum force of static friction. The force of the kinetic friction is
smaller than that of maximum static friction, but Fg remains the same.
A uniform disk, a uniform hoop, and a uniform solid sphere where are relased at the same time at the top of an inclined ramp. They all roll without slipping. The order that they reach the bottom of the ramp is the
sphere, disk, and hoop.
Two identical stones are dropped from rest and feel no air resistance as they fall. Stone A is dropped from height h, and stone B is dropped from height 2h. If the stone A takes time t to reach the ground,
stone B will take time t√(2).
An object is moving constant non-zero acceleration along the +x-axis. A graph of the velocity in the x direction as a function of time for this object is a
straight line making an angle with the time axis.
A string is attached to the rear-view mirror of a car. A ball is hanging at the other end of the string. The car is driving around in a circle, at a constant speed. What are the forces in action?
tension and gravity
Planet Z-34 has a mass equal to 1/3 that of Earth, a radius equal to 1/3 that of Earth, and an axial spin rate 1/2 that of Earth. With g representing, as usual, the acceleration due to gravity on the surface of Earth,
the acceleration due to gravity on the surface of Z-34 is 3g.
A ball is tossed vertically upward. When it reaches its highest point (before falling back downward) the velocity is zero,
the acceleration is directed downward, and the force of gravity acting on the ball is directed downward.
Tension decreases if
the angle decreases.
A player hits a ball with a bat. The action force is the impact of the bat against the ball. The reaction to this force is
the force that the ball exerts on the bat.
The more mass an object has,
the greater its inertia and the more force it take to change its state of motion.
The angular momentum about the center of the planet and the total mechanical energy will be conserved regardless of whether
the object moves from small R to large R (like a rocket being launched) or from large R to small R (like a comet approaching the earth).
An object is propelled along a straight-line path by a force. If the net force were doubled,
the object's acceleration would be twice as much.
You throw a ball. Air resistance on the ball is negligible. The functions that change the time as the ball flies through the air is
the position and velocity of the ball.
A ball is lodged in a hole in the floor near the outside edge of a merry-go-round that is turning at constant speed. The variables that change with time, assuming that the position is measured from an origin at the center of the merry-go-round, are
the position, velocity, and acceleration of ball.
If no external forces are acting on a moving object, it will continue moving at
the same velocity.
Two factors that greatly affect air resistance on falling objects are
the size and speed of the object.
A solid sphere, solid cylinder, and a hollow pipe all have equal masses and radii and are of uniform density. If the three are released simultaneously at the top od an inclined plane and roll without slipping,
the solid sphere would be the first to reach the bottom.
When throwing a ball upwards, the velocity at the highest point is
zero.
A large truck collides head-on with a cyclist. During the collision, the truck exerts the same amount of force on the cyclist as the cyclist exerts on the truck. During the collision,
the truck exerts the same amount of force on the cyclist as the cyclist exerts on the truck.
A man pushes against a rigid, immovable wall. If the man pushes on the wall with a force of 200 N, we can be sure that
the wall is pushing back with a force of exactly 200 N on him.
A box of mass m is pulled with a constant acceleration a along a horizontal frictionless floor by a wire that make an angle of 15° above the horizontal. If T is the tension in this wire,
then T > ma.
Tension remains unchanged if
there is a greater constant velocity.
The moment of inertia depends on
total mass, shape and density of the object, and the location of the axis of rotation.
If the torque of an object adds up to zero, the object could be both
turning and accelerating linearly.
A box of mass m is pressed against (but is not attached to) an ideal spring of force constant k and negligible mass, compressing the spring a distance x. After it is released, the box slides up a frictionless incline as shown in the figure and eventually stops. If we repeat this experiment, but instead compress the spring a distance of 2x just as it moves free of the spring, the box will be traveling
twice as fast as before.
Two stones, one of mass m and the other of mass 2m, are thrown directly upward with the same velocity at the same time from ground level and feel no air resistance. At its highest point, the heavier stone will have
twice as much gravitational potential energy as the lighter one because it is twice as heavy.
A stalled car is being pushed up a hill at constant velocity by three people. The net force on the car is
zero.
For a suspended object at rest, the forces acting upward on the object must be balanced by other forces acting downward to make the vector sum equal
zero.
If a car is moving left with constant velocity, one can conclude that the net force exerted on the car is
zero.
The force required to maintain an object at a constant velocity in free space is equal to
zero.
The kinetic energy of the block reaches its maximum when the displacement of the block is
zero.