Science exam
It takes 40 J to push a large box 4 m across a floor. Assuming the push is in the same direction as the move, what is the magnitude of the force on the box?
10
A machine puts out 100 Watts of power for every 1000 Watts put into it. The efficiency of the machine is
10%
The force of friction on a sliding object is 10 N. The applied force needed to maintain a constant velocity is?
10N
The force of friction on a sliding object is 10 newtons. The applied force needed to maintain a 31) constant velocity is
10N
If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by about
10m/s
A tow truck exerts a force of 3000 N on a car, accelerating it at 2 meters per second per second. 34) What is the mass of the car?
1500kg
A car moves 4 times as fast as another identical car. Compared to the slower car, the faster car has
16 times the KE
If a projectile is fired straight up at a speed of 10 m/s, the total time to return to its starting position is about
2 seconds
A car has a mass of 1000 kg and accelerates at 2 meters per second per second. What is the 33) magnitude of the net force exerted on the car?
2000N
Two projectiles are fired from ground level at equal speeds but different angles. One is fired at an angle of 30 degrees and the other at 60 degrees. The projectile to hit the ground first will be the one fired at (neglect air resistance)
30 degrees
If a rocket initially at rest accelerates at a rate of 50 m/s2 for one minute, its speed will be
3000m/s
A TV set is pushed a distance of 2 m with a force of 20 N. How much work is done on the set?
40 J
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?
400N
At one instant a heavy object in air is moving upward at 50 meters per second. One second later its speed is approximately
40m/s
A person is attracted toward the center of Earth by a 500-N gravitational force. The Earth is attracted toward the person with a force of
500
Using 1000 J of work, a toy elevator is raised from the ground floor to the second floor in 20 seconds. The power needed to do this job was
50W
An object is pulled northward by a force of 10 N and at the same time another force of 15 N pulls it 30) southward. The magnitude of the resultant force on the object is
5N
If a car increases its velocity from zero to 60 km/h in 10 seconds, its acceleration is
6km/h/s.
A block is dragged without acceleration in a straight-line path across a level surface by a force of 6N. What is the force of friction between the block and the surface?
6n
A projectile is launched at ground level an angle of 15 degrees above the horizontal and lands down range. What other projection angle for the same speed would produce the same down-range distance?
75 degrees
A 2-kg mass is held 4 m above the ground. What is the approximate potential energy of the mass with respect to the ground?
80 J
It takes 6 seconds for a stone to fall to the bottom of a mine shaft. How deep is the shaft?
About 180m
Disregarding air resistance, objects fall with constant
Acceleration
If the mass of an object does not change, a constant net force on the object produces constant
Acceleration
Without air resistance, a projectile fired horizontally at 8 km/s from atop a mountain would
All of the
Which has zero acceleration? An object
All of these
According to Newton's law of inertia, a railroad train in motion should continue going forever even if its engine is turned off. We never observe this because railroad trains
Always have forces that oppose their motion
A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always
Directed downward
The two measurements necessary for calculating average speed are
Distance and time
The newton is a unit of
Force
If an object falling freely were somehow equipped with an odometer to measure the distance it travels, then the amount of distance it travels each succeeding second would be
Greater than the second before
An object following a straight-line path at constant speed
Has zero acceleration
When an automobile is braked to a stop, its kinetic energy is transformed to
Heat
Two objects move toward each other because of gravity. As the objects get closer and closer, the force between them
Increases
If one object has twice as much mass as another object, it also has twice as much
Inertia
An object may have potential energy because of its
Location
Compared to the period of satellites in orbit close to the Earth, the period of satellites in orbit far 99) from the Earth is
Longer
A kilogram is a measure of an object's
Mass
A large metal ball is shot from a cannon with a short barrel. If the same ball were to be shot from cannon with a longer barrel, its muzzle velocity would be
More
An object that has kinetic energy must be
Moving
While a car travels around a circular track at a constant speed, its
None of the above
Acceleration is greater for a satellite when it is at the
Perigee
Both a 50-kg sack is lifted 2 meters from the ground and a 25-kg sack is lifted 4 meters in the same time. The power expended in raising the 50-kg sack is
The same
Compared to the mass of a certain object on Earth, the mass of the same object on the moon is
The same
The ball rolling down an incline has its maximum potential energy at
The top
An object is propelled along a straight-line path by a force. If the net force were doubled, the 29) object's acceleration would be
Twice as much
If an object is raised twice as high, its potential energy will be
Twice as much
A 1000-kg car and a 2000-kg car are hoisted the same distance. Raising the more massive car requires
Twice as much work
While an object near the Earth's surface is in free fall, its
Velocity Increases
A Mack truck and a Volkswagen traveling at the same speed have a head-on collision. The vehicle that undergoes the greatest change in velocity will be the
Volkswagen
Passengers in a high-flying jumbo jet feel their normal weight in flight, while passengers in the orbiting space shuttle do not. This is because passengers in the space shuttle are
Without support forces
A car maintains a constant velocity of 100 km/hr for 10 seconds. During this interval its acceleration is
Zero
When a falling object has reached its terminal velocity, its acceleration is
Zero
Which of the following has the largest momentum relative to the Earth's surface?
a pickup truck speeding along a highway
When you jump from an elevated position you usually bend your knees upon reaching the ground. By doing this, you make the time of the impact about 10 times as great as for a stiff-legged landing. In this way the average force your body experiences is
about 1/10 as great
Which of the following is not a compound?
air
The circular path of a satellite orbiting the Earth is characterized by a constant
all of these
The amount of gravitational force that acts on the space shuttle while in orbit is
almost as much as the shuttle's weight on the Earth's surface
Inside a freely falling elevator, there would be no
apparent weight for you
An archer shoots an arrow. Consider the action force to be the bowstring against the arrow. The reaction to this force is the
arrow's push against the bowstring
A bullet fired horizontally from a rifle begins to fall
as soon as it leaves the barrel
Neglecting friction, a large block of ice and a small block of ice start sliding down an incline 37) together. The heavier block will get to the bottom
at the same time as the light block.
Earth satellites are typically more than 100 km high so as to be above the Earth's
atmosphere
A very massive object A and a less massive object B move toward each other under the influence of gravitation. Which force, if either, is greater?
both forces are the same
You're driving down the highway and a bug spatters into your windshield. Which undergoes the greater change in momentum during the time of contact?
both the same
If no external forces are acting on a moving object, it will
continue moving at the same velocity
Suppose a particle is being accelerated through space by a 10-N force. Suddenly the particle encounters a second force of 10 N in the opposite direction from the first force. The particle with both forces acting on it
continues at the speed it had when it encountered the second force
A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, neglecting air drag, its vertical component of velocity
decreases
According to Newton, doubling the distance between two interacting objects
divides by 4 the gravitational force between them
An object is placed exactly halfway between the Earth and moon. The object will fall toward the
earth
According to Kepler's laws, the paths of planets about the sun are
ellipses
A vertically oriented rocket that is somehow able to maintain a continuous upward velocity of 8 km/s will
escape from the Earth.
The force that accelerates a rocket in outer space is exerted on the rocket by the
exhaust gases
Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the tendency of the rock is to
follow a straight-line path
An Earth satellite is simply a projectile
freely falling around the earth
A heavy truck and a small car rolling down a hill at the same speed are forced to stop in the same amount of time. Compared to the force that stops the car, the force needed to stop the truck is
greater
According to Newton, the greater the masses of interacting objects, the
greater the gravitational force between them
A skydiver's terminal velocity will be greatest if she falls
head first
If your automobile runs out of fuel while you are driving, the engine stops but you do not come to an abrupt stop. The concept that most explains why is
inertia
For an action force, there must be a reaction force that
is exactly equal in magnitude
The main reason ocean tides exist is that the pull of the moon
is greater on oceans closer to the moon and less on oceans farther from the moon
A ball is thrown upwards and caught when it comes back down. In the presence of air resistance, 20) the speed with which it is caught is always
less than the speed it had when thrown upwards.
A force is a vector quantity because it has both
magnitude and direction.
An astronaut , floating alone in outer space, throws a baseball. If the ball floats away at a speed of 20 meters per second, the astronaut will
move in the opposite direction, but at a lower speed.
An Earth satellite is in an elliptical orbit. The satellite travels fastest when it is
nearest the Earth
If you push for a half hour or a whole hour against a stationary wall
no work on the wall is done in either case
A satellite in an elliptical orbit travels at constant
none of these
The period of a satellite, the time it takes for a complete revolution, depends on the satellite's
radial distance
A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, neglecting air drag, its horizontal component of velocity
remains unchanged
A rifle recoils while firing a bullet. The speed of the rifle's recoil is small because the
rifle has much more mass than the bullet
Two factors that greatly affect air resistance on falling objects are the
size and speed of the object
If we doubled the magnifying power of the most powerful optical microscope in the world, we would
still not be able to see or photograph an atom
Your weight is
the gravitational attraction force between you and the Earth.
A rocket becomes progressively easier to accelerate as it travels upward from the ground mainly because
the mass of the rocket decreases as fuel is burned.
If less horizontal force is applied to a sliding object than is needed to maintain a constant velocity
the object eventually slides to a stop
The speeds of the planets about the sun depend on
their distances from the sun
Planets would crash into the sun if it weren't for
their tangential velocities
If you do work on an object in one-third the usual time, your power output is
three times the usual power output.
To catch a ball, a baseball player extends the hand forward before impact with the ball and then lets 51) it ride backward in the direction of the ball's motion. Doing this reduces the force of impact on the player's hand principally because the
time of impact is increased
When a rock thrown straight upwards gets to the exact top of its path, its
velocity is zero and its acceleration is about 10 meters per second per second.