SCI 190 Exam 1 Pretest , SCI 190: Past Quizzes , SCI 190 Exam 3 Practice Exam, SCI 190 Exam 2 Review , SCI 190: Exam 4 Review
A bullet fired horizontally over level ground hits the ground in 0.5 second. If it had been fired with twice the speed in the same direction, it would have hit the ground in
.5 s
An object covers a distance of 8 meters in the first second of travel, another 8 meters during the next second, and 8 meters again during the third second. Its acceleration in meters per second per second is approximately
0
Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet?
0
A 1-kg ball is thrown at 20m/s straight upward. Neglecting air resistance, the net force that acts on the stone when it is halfway to the top of its path is 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
Disregarding air drag, how fast must you toss a ball straight up in order for it to take 2 seconds to return to the level from which you tossed it?
10 m/s
What is the gain in speed each second for a freely falling object?
10 m/s
A push on a 1-kg brick accelerates it. Neglecting friction, to equally accelerate a 10-kg brick, one would have to push with
10 times as much force
An object released from rest on another planet requires one second to fall a distance of 6 meters. What is the acceleration in meters per second per second due to gravity on this planet?
12
An object is dropped and freely falls to the ground with an acceleration of 1 g. If it is thrown upward at an angle instead, its acceleration will be
1g downward
The brakes of a speeding truck are slammed on and it skids to a stop. If the truck were heavily loaded so that it had twice the total mass, the skidding distance would be
2 times as far
A ball players wishes to determine pitching speed by throwing a ball horizontally from an elevation 5m above ground level. The ball lands 20m downrange. The player's pitching speed is about
20 m/s
An object, at rest near the surface of a distant planet, start to fall freely. If the acceleration there is twice that of the earth, its speed one second later would be
20 m/s
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
A projectile is fired into the air at an angle of 50 degrees with the ground and lands on a target that is at the same level at which the projectile started. It will also land on the target if it is fired at an angle of
40 degrees
A vehicle that weighs 4000 N on the surface of the Earth is travelling in outer space at a speed of 200 m/s. The smallest constant force that must be applied to stop it in 20 seconds is
4000 N
One half second after starting from rest, a freely-falling object will have a speed of about
5 m/s
A 10-kilogram block with an initial velocity of 10 m/s slides 10 meters across a horizontal surface and comes to rest. It takes the block 2 seconds to stop. The stopping force acting on the block is about
50 N
A projectile is launched completely vertically upward at 50m/s. If air resistance is negligible, its speed upon returning to its starting point is
50 m/s
A skydiver, who weighs 500 N, reaches terminal velocity of 90km/h. The air resistance on the diver is then
500 N
When a woman stands at rest with both feet on a scale, it reads 500 N. When she gently lifts one foot, the scale reads
500 N
If a car accelerates from rest at 2 meters per second per second, its speed 3 seconds later will be about
6m/s
A 10.0 N force is pulling up on the ring of spring scale that weighs 2.0 N. If an 8.0 N mass is attached to the bottom hook of the scale, the scale reading would be
8 N
A man leans over the edge of a cliff and throws a rock upward at 4.9 m/s. How far below the level from which it was thrown is the rock 2 seconds later (use 9.8 m/s2 as the gravitational acceleration for this problem)
9.8 m
A focal point of the elliptical path that a satellite follows is
Earth's center
If one object has twice as much mass as another object, it also has twice as much
Inertia
Compared to a 1 kg block of solid iron, a 2kg block of solid iron has twice as much
Mass, volume, inertia
If the net force on a moving mass is zero, what can you conclude about the momentum of the moving mass?
Momentum is constant
SHORT ANSWER Bull's Eye Bob at hunting range fires his rifle at a target 200m downrange. The bullet moves horizontally from the rifle barrel with a speed of 400 m/s. how far does the bullet drop from a straight-line horizontal path by the time it reaches the target?
Time during which the bullet travels is = 0.5 s. So distance fallen is = 1⁄2gt2 = 1⁄2(10 m/s2)(0.5 s)2 = 1.25 m.
SHORT ANSWER Why do you lurch forward in a bus that suddenly slows? Why do you lurch backward when it pick up speed? What law applies here?
When the bus slows, you tend to keep moving at the previous speed and you lurch forward. When the bus picks up speed, you tend to keep moving at the previous (lower) speed and you lurch backward. The law of inertia applies in both cases.
You kick a smooth flat stone out on a frozen pond. The stone slides, slows down and eventually stops. You conclude that:
a net force acted on it all along
SHORT ANSWER 1. a. For a freely falling object dropped from rest, what is the acceleration at the end of the fifth second of fall? b. Suppose that this free-falling object was somehow equipped with a speedometer, what would be its reading after the fifth second? c. Suppose that this free-falling object was also equipped with an odometer, would the distance fallen each second indicate equal or different falling distances for successive seconds? d. What would this odometer reading be after 5 seconds?
a. The acceleration of free fall (since it is free from the effects of air resistance)at the end of the fifth, tenth, or any number of seconds is g. b. Its velocity has different values at different times, v (t =5s) = 50 m/s. c. Distance readings would indicate greater distances fallen in successive seconds. During each successive second the object falls faster and covers greater distance. d. y = vot + ½ g t2 = 0 (5) + ½ (10m/s2) (5)2 = 125m
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
A pot falls from a ledge and hits the ground 45 m below. The speed with which it hits the ground is
about 30 m/s
Hang from a pair of gym rings and the upward support forces of the rings will always
add up to equal your weight
A rock is thrown vertically into the air. At the very top of its trajectory the net force on it is
almost equal to its weight
According to Newton's Law of inertia, a rail road 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
According to Newton's law of inertia, a rail road 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
An archer shoots an arrow. Consider the action force to be exerted by 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
Which has zero acceleration? An object
at rest, moving at constant velocity, in mechanical equilibrium
A space shuttle orbits about 200 km above Earth's curve so as to be above Earth's
atmosphere
An airplane flies at 40 m/s at an altitude of 50 meters. The pilot drops a heavy package which falls to the ground. Where, approximately, does the package land relative to the plane's new position?
beneath the plane
A ball rolls off the edge of a table at the same time another ball drops vertically from the same table. The ball to hit the floor first is the
both hit at the same time
A hunter on level ground fires a bullet at an angle of 2 degrees below the horizontal while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground first?
both hit at the same time
A glass falls on to the floor. Which will have the higher change in momentum: if it hits the carpeted floor or a hard cement floor?
carpeted floor
If an object moves with constant acceleration, its velocity must
change by the same amount each second
The work done by gravity is zero for a satellite traveling in a
circular orbit
Energy is conserved when an Earth satellite travels in a
circular orbit + elliptical orbit
A satellite in elliptical orbit about Earth travels fastest when it moves
close to Earth
If no external forces are acting on a moving object it will
continue moving at the same velocity
Consider a cart on a horizontal frictionless table. Once the cart has been given a push and released, what will happen to the cart?
continue with constant 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, its vertical component of velocity
decreases
A bullet is dropped from the top of the Empire State Building while another bullet is fired downward from the same location. Neglecting air resistance, the acceleration of
each bullet is 9.8 meters per second per second
Kepler is credited as being the first to discover that the paths of planets around the Sun are
ellipses
A rock is thrown vertically into the air. At the very top of its trajectory the net force on it is
equal to its weight
A vertically oriented rocket that is somehow able to maintain a continuous upward velocity of 8 k/m will
escape from the Earth
A player catches a ball. Consider the action force to be the impact of the ball against the player's glove. The reaction to this force is the
force the glove exerts on the ball
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 with the force that stops the car, the force needed to stop the truck is
greater
Consider a ball resting in the middle of a cart. When you quickly jerk the cart forward, the ball
hits the back of the cart
When you relax at rest with your left foot one bathroom and your right foot on a similar scale, each of the scales will,
indicate different values that will equal your weight when added together
If one object has twice as much mass as another object, it also has twice as much
inertia
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
When dishes remain on a table when you yank away a tablecloth, you're illustrating
inertia
You put your book on the bus seat next to you. When the bus stops suddenly, the book slides forward off the seat. Why?
inertia caused it to move
Wherever there is an action force, there must be a reaction force which
is exactly equal in magnitude
Whenever the net force on an object is zero, its acceleration
is zero
When you are in the way of a fast-moving object and can't get out of its way, you will suffer a smaller force of impact if you decrease its momentum over a
long time
An object maintins a constant acceleration unless there is a change in its
mass, applied force, air resistance
If the acceleration of a moving mass is zero, what can you conclude about the momentum of the moving mass?
momentum is constant
If the net force a moving mass is zero, what can you conclude about the momentum of the moving mass? (think about the velocity of the moving mass)
momentum is constant
A car traveling along the highway needs a certain amount of force exerted on it to stop. More stopping force may be required when the car has
more mass, more momentum, less stopping distance
An astronaut floating alone in outer space throws a baseball. If the ball moves away at 20 m/s, the astronaut will
move in the opposite direction, but at a lower speed
When a rocket ship accelerating in outer space runs out of fuel it
no longer accelerates
A jumbo jet has a mass of 100,000 kg. The thrust for each of its four engines is 50,000 N. What is the jet's acceleration in meters per second per second when taking off?
none of these
A skydiver falls towards the Earth. The attraction of the Earth on the diver pulls the diver down. What is the reaction to this force?
none of these
A piece of clay moving with one unit of momentum strikes and sticks to a heavy bigwig ball initially at rest. After the clay sticks, both the clay and ball ideally move with a combined momentum of
one unit
When a projectile achieves escape speed from earth, it
outruns the influence of Earth's gravity but is never beyond it
As a ball falls, the action force is the pull of the Earth's mass on the ball. The reaction force is the
pull of the ball's mass on the Earth
When both the force and time of contact are doubled, the impulse on an object is
quadrupled
As soon as a bowling ball rolls off the edge of a table its horizontal component of velocity
remains constant
A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, its horizontal component of velocity
remains unchanged
When a falling object bounces as it hits the ground
the impulse on it is greater than for stopping it + its change in momentum is greater than for stopping.
Strange as it may seem, it is just as hard to accelerate a car on a level surface on the moon as it is here on the Earth. This is because
the mass of the car is independent to gravity
The fastest moving planet in a solar system is
the planet nearest the sun
A feather and a coin will have equal accelerations when falling in a vacuum because
the ratio of each object's weight to its mass is the same
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
A fore of 1 N accelerates a mass of 1 kg at the rate of 1 m/s^2. The acceleration of a mass of 2 kg acted upon by a net force of 2N.
the same
Drop a rock from a 5-m height and it accelerates at 10 m/s2 and strikes the ground 1 s later. Drop the same rock from a height of 2.5 m and its acceleration of fall is about
the same amount
An automobile and a mosquito traveling towards one another collide head-on. The collision force is
the same for both
A book is lying at rest on a table. The book will remind there at rest because
there is no net force on the book
The Earth pulls on the moon. Similarly the moon pulls on the Earth, evidence that
these two pulls comprise an action- reaction pair
Kepler is famous for finding an important relationship between a satellite's radial distance and its
time to complete an orbit
A hockey puck slides on ice at constant velocity. What is the net force acting on the puck?
zero
The force required to maintain an object at a constant velocity in free space is equal to
zero
When a falling object has reached its terminal velocity, its acceleration is
zero
SHORT ANSWER What two forces are acting on a person who stands still on the ground? Are these forces equal and opposite? Do they form an action reaction pair? Why or why not?
· Downward pull of gravity and the upward support of the floor. · Yes, for the man is in equilibrium. · No, because the two forces act on the same body. Action: Earth pulls down on man (by gravity). Reaction: man pulls up on Earth. Here we see the action-reaction pair of forces acting on different objects—man and Earth.
SHORT ANSWER 1. What is the acceleration of a rock at the top of its trajectory when it has been thrown straight upwards? Is the rock in mechanical equilibrium when it is at this highest point of its trajectory? Is your answer consistent with the Newton's Second Law, show your reasoning for the answer?
· The acceleration at the top or elsewhere in free fall is g, 10 m/s2, downward. · at the highest point of its trajectory the only force on a tossed rock, except for air resistance (which is negligible for a rock), is mg. So, the rock is not in mechanical equilibrium. · Yes. Acceleration is the ratio force/mass (Newton's second law), which in free fall is just weight/mass = mg/m = g. Since weight is proportional to mass, the ratio weight/mass is the same whatever the body · weight.
SHORT ANSWER Gravity on the surface of the moon is only 1/6 as strong as gravity on Earth. What is the weight of a 10 kg object on the Moon and on Earth? What is its mass on each? What will happen to the weight reading on a scale you stand on (On Earth) when you toss a heavy object upward?
· The weight of the 10kg mass on Earth= 10 kg × 10 m/s2 = 100 N · The weight of the 10kg mass on the Moon= 10 kg × 10/6 m/s2 = 16.7 N · Mass is 10kg, both on the Earth and on the Moon. · The scale reading will increase during the throw. Your upward force on the heavy object is · transmitted to the scale.