Reading Questions: ch. 6, 7, 8, and 9
Newton's law of gravity describes the gravitational force between _________.
- Earth and the sun. - A person and the earth. - Earth and the moon. - The sun and the planets.
For a person riding a roller coaster who is upside down at the top of a loop-the-loop, which of the following statements are true? Choose all that apply.
- The normal force from the seat on the person points downward. - The magnitude of the normal force from the seat on the person depends on how fast the person is moving.
A firecracker sitting on the ground explodes into two pieces. Immediately after the explosion, one of the pieces has momentum of 0.5 kg·m/s in the east direction. What is the momentum of the other piece?
0.5 kg·m/s west The momentum of the two pieces before the explosion was zero, so after the explosion, the total momentum must still be zero.
A force of 10 N stretches a particular spring by 2 cm. How far would a 20 N force stretch that same spring?
4 cm Notice that the amount stretched is linear with the amount of force applied; double the force and the stretch distance also doubles.
In the video, we looked at the problem of balancing a pencil on your fingertip, which is easy for a long pencil, hard for a short pencil. If you consider a long and a short pencil tipped to the side, the __________ of the shorter pencil is larger.
Angular acceleration
In the video, the two stuffed animals that rode on the turntable had the same __________ but had different __________.
Angular velocity velocity
For an extended object, the weight force can be considered to act at which point?
At the center of gravity of the object
A passenger on a carnival ride rides in a car that spins in a horizontal circle as shown at right. At the instant shown, which arrow gives the direction of the net force on one of the riders?
D the arrow facing to the left
An object is in static equilibrium if __________.
Fnet = 0 and Tnet = 0
Springs can stretch; so can different materials, including
Glass Rubber Steel
The total momentum of a system is conserved __________.
If no external forces act on the system
When we draw a diagram of the forces acting on an extended object, the tail of the force vector for the weight should be at
The Object's center of gravity
If you kick a ball, you apply an impulse. The impulse is equal to
The change in momentum of the ball.
Part complete The equation for the speed of a satellite in a circular orbit around the Earth depends on mass. Which mass?
The mass of the Earth
When we say that momentum is "conserved," we mean
The momentum of an isolated system is constant.
For an object to be in static equilibrium, the net force must be equal to zero and
The net torque must be equal to zero.
For an object in uniform circular motion, what can you say about the directions of the velocity, acceleration, and net force vectors?
The velocity vector is perpendicular to the acceleration vector; the acceleration vector is parallel to the net force vector.
Astronauts on the International Space Station feel weightless because
Their apparent weight is zero.
In the video, a car rounding a corner and a car going over the crest of a hill are both presented as examples of
Uniform circular motion.
A very rigid material—one that stretches or compresses only slightly under large forces—has a large value of __________.
Young's modulus
Hooke's law describes the force of _____.
a spring
When a car turns a corner on a level road, which force provides the necessary centripetal acceleration?
friction
For uniform circular motion, the acceleration __________.
is directed toward the center of the circle
An object will be stable if __________.
its center of gravity lies over its base of support
The units of linear momentum are _________.
kg * m/s Because momentum is mass times velocity, it has units of kg times m/s.
If you are performing the weightlifting exercise known as the strict curl, the tension in your biceps tendon is __________.
larger than the weight you are lifting
An object's angular momentum is proportional to its __________.
moment of inertia
In an inelastic collision,
momentum is conserved
If an object is rotating clockwise, this corresponds to a _____ angular velocity.
negative
The angular displacement of a rotating object is measured in _____.
radians
A net torque applied to an object causes __________.
the angular velocity of the object to change
In the impulse approximation, __________.
the external forces acting during a collision can be neglected
Which factor does the torque on an object NOT depend on?
the object's angular velocity
Moment of inertia is ________.
the rotational equivalent of mass
