Chapter 2, Earth Space Science
An object is in free fall. At one instant, it travels at a speed of 50 m/s. Exactly 1 second later, its speed is about
60 m/s
A car accelerates at 2 meters/s/s.What is its speed 3 seconds after the car starts moving?
6m/s
Which has the greatest density: 1 kg of feathers, 1 kg of lead, 10 kg of feathers?
1 kg of lead
The vertical height attained by a basketball player who achieves a hang time of a full 1 s is about
1.2 m
A 1-kg mass at Earth's surface weighs about
10 N
The force of friction on a sliding object is 10 N/ The applied force needed to maintain a constant velocity is
10 N
When a 10-N object is suspended at rest by a vertical strand of rope, the tension in the rope is
10 N
A pot falls from a ledge and hits the ground 45 m below. The speed with which is hits the ground is about
30 m/s
A man weighing 800 N stands at rest on two bathroom scales so that one scale shows a reading of 500 N. The reading on the other scale is
300 N
If a baseball being thrown goes from zero to 30 m/s in 0.1 s, what is its average acceleration?
300 m/s^2
An apple falls from a tree and hits the ground 5 m below. It hits the ground with a speed of about
10 m/s
Disregarding air drag, how fast must you toss a ball straight upward in order for the ball to remain in the air for a total time of 2 s?
10 m/s
Neglecting air resistance, when you toss a rock upward, by about how much does its upward speed decrease each second?
10 m/s
The gain in speed each second for a freely falling object is about
10 m/s.
If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by
10 m/s..
A ball is thrown 125 m upward and then falls the same distance back to the Earth. Neglecting air resistance, its total time in the air is about
10 seconds
Ten seconds after starting from rest, a free falling object on Earth will have a speed of about
100 m/s
How much tension is there in a rope that holds a 13 N bag of apples at rest?
13N
The average speed of a horse that gallops a distance of 10 km in a time of 30 min is
20 km/h
A man weighing 800 N stands at rest on two bathroom scales so that his weight is distributed evenly over both scales. The reading on each scale is
400 N
An object is pulled with two forces: 5 N North and 10 N South. The magnitude of the net force is (opposites SUBTRACT)
5 N
Suppose a jumper claims a hang time of 2 s. Then that jumper must be able to jump at a height of
5 m
One half after starting from rest, a freely falling object will have a speed of about
5 m/s
A freely falling object has a speed of 40 m/s at one instant. Exactly one second later it's speed will be
50 m/
An object is pulled northward with a force of 10 N and southward with a force of 15 N. The magnitude of the net force on the object is
5N
If a car increases its velocity from 0 to 60 km/h in 10 s, its acceleration is
6 km/h*s
What equation shows the relationship among velocity, time, and acceleration?
Acceleration=change in velocity/time interval
Did Aristotle believe that forces are necessary to keep moving objects moving, or did he believe that, once moving, they would move more themselves?
Aristotle believed that forces are necessary to keep objects moving.
What quantities are necessary to determine a vector quantity?
Direction and magnitude
Which dominated Galileo's way of extending knowledge, philosophical discussion or experiment?
Experiment
The scientist to first introduce the concept of inertia was
Galileo
What is the name of the property of objects to maintain their states of motion?
Inertia
Does the speedometer on a vehicle show average speed or instantaneous speed?
Instantaneous speed
Where would your mass be greater, on the moon or on Earth?
Mass is the same everywhere.
What were Aristotle's two main classifications of motion?
Natural and Violent motion
Which has the greater density, 1kg of water or 10kg of water?
Neither, since any amount of water has the same density.
One kg weighs N on earth. Would it weight more or less on the moon?
One kg would weight less on the moon
How does the direction of a friction force compare with the direction of motion of a sliding object?
The direction of friction is opposite to the direction of motion.
If we push a crate at a constant velocity, how does the friction on the crate compare with out pushing force? The pushing force and the surface are horizontal.
The friction force acting on the crate is equal to the pushing force and has the opposite direction.
When you toss a ball upward, by how much does its upward speed decrease each second?
The speed decreases by 10 m/s each second
When you weigh yourself, how does the support force of the scale acting on you compare with the gravitational force between you and Earth?
The support force is equal to the gravitational force and has the opposite direction
Why does the unit of time appear twice in the definition of acceleration?
The unit of time appears once for the unit of velocity, and again for the time during which the velocity changes.
What does ⅀F = 0 mean?
The vector sum of all the forces that act on an object equals zero. The forces cancel!
Why do we say that velocity and speed is not a vector?
Velocity involves both magnitude and direction. Speed involves only magnitude.
Which depends on gravity, weight or mass?
Weight
Suppose you push on a heavy crate, but not hard enough to make it slide. Does a friction force act on the crate?
Yes, opposite to your push, just enough so that f=0
Suppose you push on a heavy crate, but not hard enough to make it slide. Does a friction act on the crate?
Yes, opposite to your push, just enough so that ⅀F =0
Where would your weight be greater, on Earth or the moon?
Your weight would be greater on Earth because its force of gravity is stronger.
Hang from a pair of gym rings and the upward support forces of the rings will always
add up to equal your weight.
An object in mechanical equilibrium is an object
at rest or moving with constant motion
An object _____ has zero acceleration.
at rest, moving at constant velocity, in mechanical equalilbrium
Which has greater mass, a king size pillow, an automobile battery, or both?
automobile battery
Drop a rock from a 5 m height and it accelerates at 10 m/s^2 and strikes the ground 1 s later. Drop the same rock from a height of 2.5 m and its acceleration of fall is
the same
A motorcycle undergoes acceleration when it
changes speed or direction
The two measurements necessary for calculating average speed are
distance and time
Whereas Aristotle relied on logic in explaining nature, Galileo relied on
experiment
If a freely falling object were somehow equipped with a odometer to measure the distance it travels, then the amount of distance it travels each succeeding seconds would be
greater than the second before
An object that has twice as much mass as another objects also has twice as much
inertia
One object has twice as much mass as another object, and also has twice as much
inertia
A bullet is dropped into a river from a very high bridge. At the same time, another bullet is fired from a gun, straight down towards the water. Neglecting air resistance, the acceleration just before striking the water
is the same for each bullet
Whenever the net force on an object is zero, its acceleration
is zero
A ball is rolling down an inclined plane. How does the distance traveled by the ball in the second half second compare with the distance traveled by the ball in the first half second?
it increases
When Galileo rolled a ball down an incline and up another incline, he found that the ball rolled nearly to
its initial height
The hang time of professional basketball players is typically
less than 1 s
A kilogram is a measure of an objects
mass
Density is the ratio of
mass/volume
What equation shows the relationship among speed, distance and time?
speed=distance covered/time traveled
Your weight is
the gravitational attraction between you and the earth
Compared with the mass of a certain object on Earth the mass of the same object on the moon is
the same
Someone standing at the edge of a cliff throws one ball straight up and another ball straight down at the same initial speed. Neglecting air resistance, the ball to hit the ground below the cliff with the greater speed will be the one initially thrown
they will both hit with the same speed.
If you push on a heavy crate to the right and it slides, what is the direction of friction on the crate?
to the left
Which direction does a table push a book resting on it?
up