exam 2 review (motion)
Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet?
0
Two identical objects in outer space have a head-on collision and stick together. If, before the collision, one had been moving at 2 m/s and the other at 1 m/s, their combined speed after the collision would be
0.5 m/s
a 10 kg block is pushed across a horizontal surface with a horizontal force of 20 N against a friction force of 10N. The acceleration of the block in meters per sec per sec in
1
The power required to exert 1 N force, over a distance of 1 m in 1 second is
1 W
A 1-kg chunk of putty moving at 1 m/s collides with and sticks to a 5-kg bowling ball initially at rest. The bowling ball and putty then move with a momentum of
1 kg m/s
a rifle of mass 2 kg is suspended by strings. the rifle fires a bullet of mass 0.01 kg at a speed of 200 m/s. the recoil velocity of the rifle is about
1 m/s
a 1 kg glider and a 2kg glider both slide toward each other at 1 m/s on an air track. they collide and stick. tje combined mass moves at
1/3 m/s
a 1-kg chunk of putty moving at 1 m/s collides with and sticks to a 5kg bowling ball that is initially at rest on a frictionless surface. the speed of the putty is
1/6 m/s
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 N
A baseball player bats a ball with a force of 1000 N. The reaction force that the ball exerts against the bat is
1000N
a car accelerates at 2 meters/s/s. Assuming the car starts from rest how far will it travel in 10 s?
100m
An apple falls from a tree and hits the ground 5 meters below. It hits the ground with a speed of about
10m/s
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?
10m/s
If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by
10m/s
Two identical 5000-kg bulldozers roll toward each other on a level road without friction (one at 1 m/s, the other at 2 m/s) Just before they collide, one has a kinetic energy of 2500 J and the other 10,000 J. At this instant their total kinetic energy is
12,500 J
a car accelerates at 2 meters per second per second. assuming the car starts from rest, how much time does it need to accelerate to a speed of 30m/s
15 seconds
a ball is moving at 3 m/s and has a momentum of 48 kg/m/s. what is the balls mass?
16 kg
a 2 kg mass has 40 J of potential energy w respect to the ground. Approx. how high is it above the ground
2 m
a 1000kg car moving at 10 m/s brakes to a stop in 5 sec. The avg braking force is
2000 N
A car has a mass of 1000 kg and accelerates at 2 meters per second per second. What is the magnitude of the net force exerted on the car?
2000N
an object at rest near the surface of a distant planet starts to fall freely. If the acceleration there is twice that of the earth its speed one second later would be
20m/s
What horizontally-applied force will accelerate a 400-kg crate at 1 m/s2 across a factory floor against a friction force half its weight?
2400 N
a 2500 N pile driver ram falls 10m and drives a post 0.1 m into the ground. The avg impact force on the ram is
250,000 N
An object falls freely from rest on a planet where the acceleration due to gravity is twice as much as on Earth. In the first 5 seconds it falls a distance of
250m
how many joules of energy are in one kilowatt hour
3.6 million
a 300 kg bear grasping a vertical tree slides down at constant velocity. the friction force between the tree and the bear is
3000N
a 1000kg automobile enters a freeway on ramp at 20m/s and acceleration uniformly up to 40m/s in a time of 10 sec. how far does the automobile travel during that time
300m
a 4 kg ball has a momentum of 12kg/m/s. what is the balls speed
3m/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 vehicle that weighs 4000 N on the surface of the Earth is traveling in outer space at a speed of 200 m/s. the smallest constant force that must be applied to stop it in 20 sec is
4000N
A piece of rope is pulled by two people in a tug-of-war. Each pulls with 400 N of force. What is the tension in the rope?
400N
At one instant a heavy object in air is moving upward at 50 m/s. One second later its speed is approximately
40m/s
Two people, one twice as massive as the other, attempt a tug-of-war with 12 meters of massless rope on frictionless ice. After a brief time, they meet. The heavier person slides a distance of
4m
a 5 kg fish swimming at a speed of 1m/s swallows an absent minded 1kg fish at rest. The speed of the larger fish after this lunch is
5/6 m/s
Using 1000 J of work, a toy elevator is raised from the ground floor to the second floor in 20 s. How much power does the elevator use?
50 W
a jack system will increase the potential energy of a heavy load by 1000 J with a work input of 2000 J. The efficiency of the jack system is
50%
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 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
A diver who weighs 500 N steps off a diving board that is 10 m above the water. The diver hits the water with kinetic energy of
5000 J
a 5000 kg freight car runs into a 10,000kg freight car at rest. They couple upon collision and move with a speed of 2m/s. what was the initial speed of the 5000 kg car?
6 m/s
At one instant an object in free fall is moving downward at 50 m/s. One second later its speed is
60m/s
If a car increases its velocity from zero to 60 m/s in 10 seconds, its acceleration is
6km/h/s
If a car accelerates from rest at 2 meters per second per second, its speed 3 seconds later will be about
6m/s
a car's engine is 20% efficient. when cruising, the car encounters an avg retarding force of 1000N. if the energy content of gas is 40 megajoules per liter how many kilometers per liter does the car get
8
a 2 kg mass is held 4m above the ground. What is the approx. potential energy of the mass w respect to the ground
80 J
If you drop an object, it will accelerate downward at a rate of 9.8 meters per second per second. If you instead throw it downwards, its acceleration (in the absence of air resistance) will be
9.8 meters per second per second
a 1kg mass at the earths surface weighs
9.8N
A skydiver of mass 100 kg experiences air resistance of 500 N, and an acceleration of
about 0.5g
When you jump from an elevated position you usually bend your knees upon reaching the ground, which makes the time of the contact about 10 times that of a stiff-legged landing. In this way the average force your body experiences is
about 1/10 as great
a ball is thrown 125 meters upwards and then falls the same distance back to earth. neglecting air resistance the total time in the air is
about 10 seconds
It takes 6 seconds for a stone to fall to the bottom of a mine shaft. How deep is the shaft?
about 180m
a package falls off a truck that is moving at 30m/s. Neglecting air resistance, the horizontal speed of the package just before it hits the ground is
about 30m/s
Disregarding air resistance, objects fall with constant
acceleration
If an object of constant mass experiences a constant net force, it will have a constant
acceleration
Hang from a pair of gym rings and the upward support forces of the rings will always
add up to equal your weight
Your friend says that the heavyweight champion of the world cannot exert a force of 50 N on an isolated piece of tissue paper with his best punch. you
agree that it cant be done
compared a 1 kg block of solid iron, a 2kg block of solid iron has twice as much
all of them
An object in mechanical equilibrium is an object
at rest moving with constant velocity having no acceleration
Which has zero acceleration? An object
at rest, moving at constant velocity, in mechanical equilibrium
Neglecting friction, a large block of ice and a small block of ice start sliding down an incline together. The heavier block will get to the bottom
at the same time as the light block
What task requires the most work; lifting a 50-kg sack 2 meters or lifting a 25-kg sack 4 meters?
both require the same amount of work
Arnold Strongman and Suzie Small each pull very hard on opposite ends of a massless rope in a tug-of-war. The greater force on the rope is exerted by
both the same, interestingly enough
If an object moves with constant acceleration, its velocity must
change by the same amount each second
If no external forces are acting on a moving object, it will
continue moving at the same velocity
according to newtons law of inertia, a railroad train in motion should continue
d
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
A freight train rolls along a track with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is
doubled
According to the impulse-momentum equation Ft = change in (mv), a person will suffer less injury falling on a wooden floor which "gives" than on a more rigid cement floor. The "F" in the above equation stands for the force exerted on the
either the force on the person or the force on the floor
a truck is moving at constant velocity. inside the storage compartment, a rock is dropped from the midpoint of the ceiling and strikes the floor. the rock hits the floor
exactly below the midpoint of the ceiling
The scientist to first introduce the concept of inertia was
galileo
Momentum is transferred to the ground when an apple falls on it. The momentum absorbed by the ground is
greater than that of an apple only if the apple bounces
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
A karate expert executes a swift blow and splits a cement block with her bare hand. the magnitude of the force experienced by her hand is
identical to the force applied to the block
Padded dashboards in cars are safer in an accident than non-padded ones because passengers hitting the dashboard has
increased time of impact
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
Whenever the net force on an object is zero, its acceleration
is zero
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
Twelve seconds after starting from rest, an object falling freely will have a speed of
more than 100m/s
When a rocket ship accelerating in outer space runs out of fuel it
no longer accelerates
Starting from rest, the distance a freely falling object will fall in 9.5 seconds is about
none of the above
a large heavy truck and a small baby carriage roll down a hill. neglecting friction, at the bottom of the hill, the baby carriage will have a greater
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 1-N apple falls to the ground. the apple hits the ground with an impact force of about
not enough info given to say
The force exerted on the tires of a car to directly accelerate it along a road is exerted by the
road
Two identical freight cars roll without friction towards each other on a level track. One car rolls at 2 m/s and the other car rolls at 1 m/s. After the cars collide, they roll in the direction that
the faster car was initially going
your weight is
the gravitational attraction between you and the earth
a rock weighs 30 N on earth. a second rock weighs 30N on the moon. which of the two have a greater mass?
the one on the moon
a force of 1N accelerates a mass of 1 kg at the rate of 1m/s/s. the acceleration of a mass of 2 kg acted upon by a net force of 2 N 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
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 object lifted 10 meters gains 200 J of potential energy. If the same object is lifted 20 meters, its potential energy gain is
twice as much
While an object near the Earth's surface is in free fall, its
velocity increases
A car maintains a constant velocity of 100 km/hr for 10 seconds. During this interval its acceleration is
zero
