PHYS 1415 (Unit 1) Ch 1-4
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
A sheet of paper can be withdrawn from under a container of milk without toppling it is the paper is jerked quickly. This best demonstrates that
the milk carton has inertia
The muzzle velocity of a certain gun is 100 m/s. Neglecting air resistance, at the end of 1 s a bullet fired straight up into the air will have traveled a distance of about
(100 - 5) m
The muzzle velocity of a certain gun is 100 m/s. Neglecting air resistance, at the end of 1 s a bullet fired straight up into the air will have traveled a distance of about
(100-5) m
An object travels 8 m in the first s of travel, 8 m again during the second s of travel, and 8 m again in the third s. Its acceleration in m/s/s is
0
A rifle of mass 2 kg is suspended by strings. The rifle fires a bullet of mass 1/100 kg at a speed of 200 m/s. The recoil velocity of the rifle is about
1 m/s
A 5 kg blob of clay moving ant 2 m/s slams into a 4 kg blob of clay at rest. The speed of the two blobs stuck together after colliding is about
1.1 m/s
A rock is thrown vertically into the air. At the top of its path, its acceleration in m/s/s is about
10
A 1-kg mass at the earth's surface weighs about
10 N
Ten seconds after starting from rest, a freely falling object will have a speed of about
100 m/s
A ball is moving at 4 m/s and has a momentum of 48 k*m/s. What is the ball's mass?
12 kg
A tow truck exerts a force of 3000 N on a car, accelerating it at 2 m/s/s. What is the mass of the car?
1500
If a power plant is 30% efficient, and the transmission system that deliver power to consumers is 60% efficient, then the overall efficiency is
18% (.3 x .6 = .18 ---> 18%)
The average speed of a horse that gallops a distance of 10 km in a time of 30 min is
20 km/h. (avg speed = distance/time)
A 4 kg ball has a momentum of 12 kg*m/s. What is the ball's speed?
3 m/s (momentum = mass x speed)
If a baseball being thrown goes from zero to 30 m/s in 0.1 s, what is its average acceleration?
300 m/s/s
A 300-kg bear grasping a vertical tree slides down at constant velocity. The friction force between the tree and the bear is
3000 N (1 kg = 10 N; 300kg = 3000 N)
If a rocket initially at rest accelerates at a rate of 50 m/s/s for 1 min, its speed will be
3000 m/s (speed = distance/time)
Two people, one twice as massive as the other, attempt a tug-of-war with 12 m of rope on frictionless ice. After a brief time, they meet. The heavier person slides a distance of
4 m
A TV set is pushed a distance of 2 m with a force of 20 N that is in the same direction as the set moves. How much work is done on the set?
40 J (work = 20 N x 2 m)
Suppose a jumper claims a hang time of 2 s. Then that jumper must be able to jump a height of
5 m
A 5 kg fish swimming at a speed of 1 m/s swallows an absent minded 1 kg fish at rest. The speed of the larger fish after 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 220 s. How much power does the elevator use?
50 W
A car accelerates from rest at 2 m/s/s. What is its speed 3 s after the car starts moving?
6 m/s
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 (PE = weight x height)
The scientist to first introduce the concept of inertia was
Galileo
A Mack truck and a Volkswagen traveling at the same speed have a head-on collision. The vehicle to undergo the greatest change in velocity will be the
Volkswagen
If your mass, the mass of the Earth, and the mass of everything in the solar system were twice as much as it is now, yet everything stayed the same size, your weight on Earth would
guadruple
An object is propelled along a straight-line path in space by a force. If the mass of the object somehow becomes twice as much, its acceleration
halves
When the distance between two stars decreases by half, the force between them
increases to four times as much
One object has twice as much mass as another objects, and also has twice as much
inertia
A force is a vector quantity because it has both
magnitude and direction
The force required to maintain an object at a constant velocity in free space is equal to
zero
A sack of potatoes weighing 200 N falls from an airplane. As the velocity of fall increases air resistance also increases. When air resistance equals 200 N, the sack's acceleration in m/s/s is
0
What is the acceleration of a car that maintains a constant velocity of 100 km/h for 10 s?
0 (constant velocity = no change = no acceleration)
A 10 N falling object encounters 10 N of air resistance. The net force on the object is
0 N
A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected, the force required to keep the puck sliding at constant velocity is
0 N
The vertical height attained by a basketball player who achieves a hang time of a full 1 s is about
1.2 m
Starting from rest, the distance a freely falling object will fall in 0.5 s is about
1.25 m (d = 1/2gt^2)
a 1 kg glider and a 2 kg glider both slide toward each other at 1 m/s on an air track. They collide and stick. The 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 5 kg bowling ball that is initially at rest. The bowling ball and putty are then set in motion with a speed of
1/6 m/s
If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by about
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 s
A machine puts out 100 W of power for every 1000 W put into it. The efficiency of the machine is
10% (E = energy out / energy in) --- 100 / 1000 = .1 = 10%
A car moves 4 times as fast as another identical car. Compared to the slower car, the faster car has
16 times the KE (KE = 1/2 mass x speed^2)
If a freely falling object were somehow equipped with a speedometer on a planet where the acceleration due to gravity is 20 m/s/s/, then its speed reading would increase each second by
20 m/s
A 1000 kg car moving at 10 m/s brakes to a stop in 5 s. The average braking force is
2000 N [force = (mass)(speed)/time] --- f = 1000 x 10/5 = 2000
If a rocket accelerates from rest at a rate of 50 m/s/s for 10 s, the distance it will cover during this time is about
2500 m (d = 1/2gt^2)
A girl pulls on a 10 kg wagon with a constant force of 30 N. What is the wagon's acceleration in m/s/s?
3.0
How many joules of energy are in 1 kWh?
3.6 MJ
A 500 N parachutist opens his chute and experiences an air resistance force of 800 N. The net force on the parachutist is
300 N upward
A car has a mass of 1000 kg and accelerates at 2 m/s/s. What is the magnitude of the force exerted on the car
500 N
An object weighs 30 N on Earth. A second object weighs 30 N on the Moon. Which has the greater mass?
the one on the moon
Two identical arrows, one with twice the kinetic energy of the other, are fired into a hay bale. The faster arrow will penetrate
twice as far as the slower arrow
A 1000 kg car and a 2000 kg car are hoisted the same distance in a gas station. Raising the more massive car requires
twice as much work
Two billiard balls having the same mass roll toward each other, each moving at the same speed. What is the combined momentum of the two balls?
0 kg*m/s
If an astronaut whose total mass is 100 kg ejects 0.1 kg of gas at a speed of 50 m/s from her propulsion pistol, her recoil speed is
0.05 m/s
A skydiver of mass 100 kg experiences air resistance of 500 N, and an acceleration of about
0.5g
A 30 kg girl and a 25 kg boy face each other on friction-free roller blades. The girl pushes the boy, who moves away at a speed of 1 m/s. The girls speed is
0.83 m/s
A 10 kg block is pushed across a horizontal surface with a horizontal force of 20 N against a friction force of 10 N. The acceleration of the block in m/s/s is
1
Exert 1 N for a distance of 1 m in 1 s and you deliver a power of
1 W (power = work done/time interval)
A 1 kg chunk of putty moving at 1 m/s collides 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 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
A jack systemwill increase the potential energy of a heavy load by no more than 1000 J with a work imput of 2000. The efficiency of the jack system is no more than
50%
A person is attracted toward the center of the Earth by a 500 N gravitational force. The force of attraction of the Earth toward the person is
500 N
Starting from rest, the distance a freely falling object will fall in 10 s is about
500 m/s (d=1/2gt^2) --- 1/2(10)(10)^2 = 5x100 = 500
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
The average momentum of a 70 kg runner who covers 400 m in 50 s is
560 kg*m/s
A 10 N falling object encounters 4 N of air resistance. The magnitude of the net force on the object is
6 N
If a car increases its velocity from zero to 60 km/h in 10 s, its acceleration is
6 km/h/s (acceleration = change in speed/time interval) --- 60/10 = 6
A car accelerates from rest ot 2 m/s/s. What is its speed 3 s after the car starts moving?
6 m/s/s
An object is in free-fall. At one instant, it travels at a speed of 50 m/s. Exactly 1 s later, its speed is about
60 m/s (free fall = 10 m/s - 50 m/s+10 m/s = 60 m/s)
An object is placed exactly halfway between the Earth and the Moon. The object will fall toward the
Earth
Arnold Strongman and Suzie Small have a tug-of war on a polished floor. Arnold wears socks and Suzie wears gym shoes. The likely winner is
Suzie
The reason a bullet has more kinetic energy than the recoiling rifle from which it is fired is because the force ont he bullet acts over a longer
distance
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
Compared with falling on a wooden floor, a wine glass may not break when it falls to a carpeted floor because of the
longer time to stop
A kilogram is a measure of an objects
mass
According to Newton, the greater the distance between masses of interacting objects, the
less the gravitational force between them
If an object has kinetic energy, then it also must have
momentum
In raising a 5000 N piano with a pulley system, it is noted that for every 1 m of rope pulled down, the piano rises 0.1 m. Ideally, this means the force needed to lift it is about
500 N
When a woman stands at rest with two feet on a scale, the scale reads 500 N. When she gently lifts one foot, the scale reads
500 N
Starting from rest, the distance a freely falling object will fall in 10 s is about
500 m
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 greatest speed will be the one initially thrown
they will both hit with the same speed
What is the force of gravity on a 500 N woman standing on Earth's surface?
500 N
Disregarding air drag, how fast must you toss a ball straight upward in order to remain in the air for a total time of 2 s?
10 m/s
Inside a freely falling elevator, there would be no
apparent weight for you
A moving object on which no forces are acting will continue to move with constant
momentum (Newton's 1st Law of Motion * Law of Inertia *)
compared with a 1-kg block of solid iron, a 2-kg block of iron has the same
none of these (weight, volume, mass)
A light woman and a heavy man jump from an airplane at the same time and open their same-size parachutes at the same time. Which person will get to a state of zero acceleration first?
the light woman
A 5 kg fish swimming at a speed of 1 m/s swallows an absent minded 1 kg fish swimming toward it at 4 m/s. The speed of the larger fish after lunch is
1/6 m/s
The impulse-momentum relationship is a direct result of
Newton's Second Law
A player hits a ball with a bat. The action force is the impact of the bat against the ball. The reaction to his force is the
force of the ball against the bat
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 (speed = distance/time) --- 5m/.5 s = 10 m/s
A ball is thrown 125 m upward and then falls the same distance back to the earth. Neglecting air resistnace, its total time in the air is about
10 s (t = *sq rt* 2d/g)
A woman who normally weighs 400 N stands on top of a very tall ladder so she is one Earth-radius above the Earths surface. How much would she weigh there?
100 N
A car accelerates at 2 m/s/s. Assuming the car starts from rest, how far will it travel in 10 s?
100 m
When you stand at rest on a pair of bathroom scales, the readings on the scales will always
add to equal your weight
A bullet is fired straight down from the top of a high cliff. Neglecting air resistance, the acceleration of the bullet in m/s/s is
g
