physics test 1

A car with a mass of 1510 kg moves at 15 m/s. What braking force is needed to bring the car to a halt in 10s?

-2265N When solving a problem of cars stopping with relation to time, this is an Impulse-Momentum problem. Ft = ∆mv, where in this case the ∆mv is just mv since the final momentum is zero. We can solve this as: F = ∆mv/t The correct answer is: -2265.00 N

A 4 kg fish swimming 8 m/s swallows an absent minded 1 kg fish swimming toward it at a velocity that bring both fish to a halt immediately after lunch. What is the velocity of the smaller fish before lunch?

-32 m/s This is a static collision problem using the equation: (m1)(v1)i + (m2)(v2)i = (m1+m2)Vf So in this case make sure you use a negative sign for the velocity of the smaller fish. They are traveling in opposite directions. Velocity is a vector which includes a direction.

A railroad engine weighs 7 times as much as a freight car. If the engine coasts at 2 km/h into a freight car that is initially at rest, how fast do the two coast after they couple together?

1.75 km/h This is another version of a collision problem: (m1)(v1)i + (m2)(v2)i = (m1+m2)Vf We don't know the mass but we know the relationship. An easy way to do problems like this is to use a variable. Let's call the mass of the freight car 'M'. The numbers are random with this problem so lets say the engine weighs 3 times as much as the freight car and is moving at 5 km/h. The equation will look like this: (3m*5) + (m*0) = (3m + m) vf vf = 15/3 = 5 The correct answer is: 1.75 m/s

If you push an object twice as far while applying the same force, you do Select one: a. the same amount of work on both. b. half as much work. c. twice as much work. d. four times as much work.

Fd=ΔW Doubling the distance will double the amount of work done. The correct answer is: twice as much work.

Describe the difference between a scientific theory and a scientific law

Theory - an explanation of an observed phenomena Law - a description of an observed phenomena

A ring and a disk of equal mass and diameter begin rolling down a hill together. The one to reach the bottom first is the a) disk b) ring c) they all reach the bottom at the same time d) not enough information is given

a

Facts in the field of science... a. are changeable b. are more important than theories c. mean very little d. are absolute

a

Horses that move with the fastest linear speed on a merry-go-round are located a) near the outside b) near the center c) anywhere because they all move at the same speed

a

In order to catch a ball, a baseball player extends the hand forward before impact with the ball and then lets it ride backward in the direction of the ball's motion upon impact. Doing this reduces the force of impact on the player's hand principally because the a) time of impact is increased b) relative velocity is less c) force of impact is reduced d) time of impact is decreased e) none of these

a

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 a) continues at the speed it had when it encountered the second force b) is brought to a rapid halt c) decelerates gradually to a halt d) theoretically tends to accelerate toward the speed of light e) none of these

a

When you stand at rest on a pair of bathroom scales, the readings on the scales will always a) add to equal your weight b) each equal your weight c) each be half your weight

a

a 4kg ball has a momentum of 12 kg m/s. what is the ball's speed? a) 3 m/s b) 4 m/s c) 12 m/s d) 48 m/s e) none of these

a

a rifle recoils from firing a bullet. the speed of a rifle's recoil is small because that a) rifle has much more mass than the bullet b) momentum is mainly concentrated in the bullet c) force against the rifle is smaller the against the bullet d) momentum of the rifle is smaller

a

if a freely-falling object were somehow equipped with an odometer to measure the distance it travels, then the amount of distance it travels each succeeding second would be a) greater than the second before b) less and less c) constant

a

the chef at the infamous fattening tower of pizza tosses a spinning disk of uncooked pizza dough into the air. the disk's diameter increases during the the flight, while its rotational speed a) decreases b) remains constant c) increases

a

what is the stopping distance of a car traveling at 60 mph compared to the stopping distance for the same car traveling at 30 mph a) 4 times b) 3 times c) the same d) 3 more car lengths

a

a kilogram is a measure of an object's a) mass b) force c) weight d) center of mass e) gravity

a) mass

If we removed the air resistance, objects would fall with constant Select one: a. acceleration. b. distances each consecutive second. c. velocity. d. speed.

a. acceleration

The two measurements necessary for calculating average speed are Select one: a. distance and time. b. acceleration and time. c. velocity and time. d. distance and acceleration. e. velocity and distance.

a. distance and time Average speed = Distance / Time

If you were to put very large diameter tires on your truck, your speedometer will measure a speed that is Select one: a. lower than it is actually. b. the same as before. c. higher than it is actually.

a. lower than it is actually You will travel further per rotation of the tire if the diameter is larger. Your car measures your speed by the number of rotations per minute your tire is rotating. So if you car things you went distance x if one minute, you have actually traveled further. For this reason your speedometer would read a speed slower than you are actually traveling. The correct answer is: lower than it is actually.

Of the sciences known as physics, chemistry, and biology, the most basic is Select one: a.physics. b.none of these. c.chemistry. d.biology.

a. physics

A sheet of paper can be withdrawn from under a cup of water without spilling if the paper is yanked out quickly. This best demonstrates that Select one: a. the cup of water has inertia. b. gravity tends to hold the cup of water secure. c. none of these. d. the cup of water has no acceleration.

a. the cup of water has inertia

A car traveling at 22 m/s comes to an abrupt halt in 0.1 second when it hits a tree. What is the deceleration of the car in meters per second per second? a) 110 b) 220 c) 800 d) 880 e) ...can't be solved without the mass of the car

b

A rock is thrown vertically into the air. at the top of its path, its acceleration in meters per second per second is a) zero b) 10 c) between 0 and 10 d) greater than 10 e) none of these

b

An object is pulled northward by a force of 10 N and at the same time another southward force of 15 N. The magnitude of the resultant force on the object is a) 0 N b) 5 N c) 10 N d) 15 N e) none of these

b

An upright broom is easier to balance when the heavier end is a) nearest your hand b) highest, farthest your hand c) same either way

b

If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by about a) 5 m/s b) 10 m/s c) 15 m/s d) a variable amount e) depends on initial speed

b

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? a) 4 N b) 10 N c) 40 N d) 160 N e) none of these

b

a 1000-kg car moving at 10 m/s brakes to a stop in 5 s. the average braking force is a) 1000 N b) 2000 N c) 3000 N d) 4000 N e) 5000 N

b

a pair of tennis balls fall through the air from a tall building. one ball is regular and the other is filled with lead pellets. air resistance just before they hit is actually greater for the a) regular ball b) lead-filled ball c) same for both

b

suppose a certain carnival has a ferris wheel where the seats are located halfway between the center and outside rim. compared to an ordinary ferris wheel where the seats on are on the outside rim, your angular speed while riding on this ferris wheel would be a) less and your tangential speed more b) the same and your tangential speed less c) more and your tangential speed less

b

when an object is raised above the ground it gains a certain amount of potential energy. if the same object is raised twice as high it gains a) four times as much potential energy b) twice as much potential energy c) neither of these

b

If a rocket accelerates from rest at a rate of 50 m/s2 for 10s, the distance it will cover during this time is Select one: a. 5000m. b. 2500m. c. 500m. d. 250m.

b. 2500 m ∆x=Vot + 1/2 ∆x=0 + 1/2 (50)(10)^2 ∆x=2500m

A bow is drawn so that it has 40 J of potential energy. When fired, the arrow will ideally have a kinetic energy of Select one: a. less than 40 J. b. 40 J. c. more than 40 J.

b. 40 J This is a conservation of momentum problem. When the arrow is released it will no longer have PE so that 40 J is converted to KE. The correct answer is: 40 J.

A heavy object and a light object are dropped at the same time from rest in a vacuum. The heavier object reaches the ground Select one: a. after the lighter object b. at the same time as the lighter object. c. before the lighter object.

b. at the same time as the lighter object If a problem does not specifically say that air resistance is ignored, you have to take it into consideration. The lighter object will reach terminal velocity first. If it weighs say 1 newton, it only needs 1 newton of air resistance before it stops accelerating. The heavier object, say 10 newton's, keeps accelerating until it reaches it terminal velocity. So it is traveling faster and will reach the ground first.

When bullets are fired from an airplane in the forward direction, the momentum of the airplane will be Select one: a. increased. b. decreased. c. unchanged.

b. decreased According to the conservation of momentum the airplane would recoil from the shots giving it slightly less momentum than before. The correct answer is: decreased.

In science, an educated guess is a Select one: a.hypothesis and theory. b.hypothesis. c.theory.

b. hypothesis

A bullet is dropped into a gorge from a high cliff. At the same time, another bullet is fired from a gun, straight down towards the base of the gorge. Neglecting air resistance, the acceleration just before striking the water Select one: a. depends on how high they started. b. is the same for each bullet. c. is greater for the fired bullet. d. is greater for the dropped bullet.

b. is the same for each bullet The question asks for acceleration. Since they are in free fall and we are ignoring air resistance, the only force is gravity. That accelerates objects in free fall at -10 m/s/s no matter how fast they are traveling.

When a rocket ship accelerating in outer space runs out of fuel it Select one: a. accelerates for a short time, then slows down to a constant velocity. b. no longer accelerates. c. accelerates for a short time, slows down and eventually stops.

b. no longer accelerates A net force must be applied to an object or its motion will not change. This motion could be zero (at rest) or 10 or 100. No matter what it is, it will not change.

When a scientist is dishonest and publishes fabricated results, they Select one or more: a.will be excused in the scientific community. b.receive no second chance and loose all respect of the scientific community.

b. receive no second chance and loose all respect of the scientific community

If a large truck loaded with bricks has a head on collision with a small car, which will experience the greater acceleration? Select one: a. the truck b. the car c. the same for both

b. the car While they experience the same force, their mass dictacts there acceleratioin. Remember that F = ma. So considering that the force is the same, if the mass is smaller, the acceleration must be larger. The correct answer is: the car

An object lifted 10 meters gains 200 J of potential energy. If the same object is lifted 20 meters, its potential energy gain is Select one: a. four times as much. b. twice as much. c. more than four times as much. d. half as much. e. the same.

b. twice as much PE=mgh. If you double the height without changing the mass, the PE will double. The correct answer is: twice as much.

To turn a really tight screw, it would be easier fi you were to choose a screwdriver that has a Select one: a. long handle. b. wide (or fat) handle. c. narrow (or skinny) handle.

b. wide (or fat) handle You apply a torque to a screwdiver when you turn it. Use a fatter handle and you increase the distance giving a larger torque, Force x distance. The correct answer is: wide (or fat) handle.

At position A, is the marble's kinetic energy less than, greater than, or the same as its kinetic energy when it is at B? (the ball is at the top and about to roll down hill) a) greater b) the same c) less

c

In each second of fall, the distance a freely falling object will fall is a) about 5 m b) about 10 m c) the same, but not 5m or 10m d) increasing e) none of these

c

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 a) 1/2 m/s b) 1/5 m/s c) 1/6 m/s d) 2/3 m/s e) 3/2 m/s

c

a baseball player bats a ball with a force of 1000 N. the ball exerts a reaction force against the a) more than 1000 N b) less than 1000 N c) 1000 N

c

a large truck and a Volkswagen traveling at the same speed collide head-on. the impact force is a) greater on the mack truck b) greater on the Volkswagen c) the same for both

c

it takes 6 seconds for a stone to fall to the bottom of a mine shaft. how deep is the shaft? a) about 60 m b) about 120 m c) about 180 m d) more than 200 m

c

If a baseball being thrown goes from zero to 60 m/s in 0.2 seconds, what is the average acceleration? Select one: a. 30 m/s2 b. 3 m/s2 c. 300 m/s2 d. 3000 m/s2

c. 300 m/s2 a=∆v/t a= (60-0)/0.2 = 300 m/s2 =300 m/s2

When doing flips off of a diving board, you'll more easily rotate when your body is Select one: a. straight as a board. b. in any orientation. c. balled up.

c. balled up Your rotational inertia is reduced when you are balled up because your radius of curvature is smaller. It is easier for something to start rotating when the rotational inertia is reduced. The correct answer is: balled up.

If a large truck loaded with bricks has a head on collision with a small car, which will experience the greater change in momentum? Select one: a. The large truck. b. The small car. c. Both will experience the same change in momentum.

c. both will experience the same change in momentum Impulse Ft is equal to the change in Momentum Δmv. The momentum has to be the same since the Impulse is the same. The correct answer is: Both will experience the same change in momentum.

If a large truck loaded with bricks has a head on collision with a small car, which will experience the greater impulse? Select one: a. The large truck. b. The small car. c. Both will experience the same impulse.

c. both will experience the same impulse Impulse is Ft. We know that the force is the same because of Newton's Third Law. We also know that the time is the same since they are touching each other. So the impulse is the same. The correct answer is: Both will experience the same impulse.

If no external forces are acting on a moving object it will Select one: a move slower and slower until it finally stops. b continue moving at the same speed. c. continue moving at the same velocity.

c. continue moving at the same velocity A net force must be applied to an object or its motion will not change. This motion couldbe zero (at rest) or 10 or 100. No matter what it is, it will not change.

A pizza chef tosses a spinning disk of uncooked pizza dough into the air. The disk's diameter increases during the flight, while its rotational speed Select one: a. remains constant. b. increases. c. decreases.

c. decreases Angular momentum mvr in this case is conserved so if the diameter, r, increases, the velocity must decrease. The correct answer is: decreases.

A train boxcar is moving at a constant velocity. Inside the storage compartment, a rock is dropped from the midpoint of the ceiling and strikes the floor below. The rock hits the floor Select one: a. more information is needed to solve this problem. b. ahead of the midpoint of the ceiling. c. exactly below the midpoint of the ceiling. d. none of these. e. behind the midpoint of the ceiling.

c. exactly below the midpoint of the ceiling Everything inside the boxcar is moving at the same velocity. So, when the rock is released, there are no forces pushing it forward or back. No net force means the rock will just fall straight down relative to the boxcar.

A scientific idea that is so well established that it can't be questioned by others is Select one: a. a law. b. a hypothesis. c. impossible. d. a theory.

c. impossible

A coin and a ring, each with the same mass, roll down an incline starting at the same time. Which one will reach the bottom first? Select one: a. It's a tie. b. The ring. c. The coin.

c. the coin The coin has is mass evenly distributed while the ring has its mass far away from the center of rotation giving it more rotational inertia. Therefore the coing will get to the bottom first everytime. The correct answer is: The coin

If a large truck loaded with bricks has a head on collision with a small car, which will experience the greater force? Select one: a. The truck b. The car c. The same

c. the same Newton's 3rd law says they will experience the same force.

A car accelerates at 2 meter per second per second. What is its speed 3 seconds after the car starts moving? a) 2 m/s b) 3 m/s c) 4 m/s d) 6 m/s e) none of these

d

A car has a mass of 1000 kg and accelerates at 2 m/s2. What is the magnitiude of net force exerted on the car? a) 500 N b) 1000 N c) 1500 N d) 2000 N e) none of these

d

An object maintains its state of motion because it has a) weight b) speed c) acceleration d) mass e) all of these

d

If a car increases its velocity from zero to 60 km/h in 10 seconds, its acceleration is a) 10 km/h/s b) 3 km/h/s c) 60 km/h/s d) 6 km/h/s e) 600 km/h/s

d

a skydiver, who weights 500 N, reaches terminal velocity of 90 km/h. the air resistance on the diver is then a) 90 N b) 250 N c) 410 N d) 500 N e) none of these

d

if a piece of sheet metal is cut into the shape shown (an L shape), its center of gravity is at a) a ( the top) b) b (the middle) c) c ( the outside corner) d) d (the inside corner)

d

a hockey puck is set in motion to across a frozen pond. if ice friction and air resistance are neglected, the force required to keep the puck sliding at constant velocity is a) the mass of the puck multiplied by 9.8 meters per second per second b) equal to the weight of the puck c) the weight of the puck divided by the mass of the puck d) zero newtons e) none of these

d) zero newtons

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? Select one: a. 4 N. b. 40 N. c. 160 N. d. 10 N.

d. 10 N Fd=ΔEnergy F=ΔE/d=40J/4m=5N The correct answer is: 10 N.

The last instant just before a free falling elevator car crashes, a passenger jumps out the door and falls only two feet to the ground. The passenger is Select one: a. intelligent to think so fast. b. unharmed. c. lucky to have studied physics. d. probably hurt or killed.

d. probably hurt or killed The elevator car and the passenger are falling with the same acceleration, We'll learn more about that later. Even though jumping up will negate some of that speed, it will be a small percentage. When striking the ground, the passenger will have to stop very fast. Their inertia will require a large force which will hurt or kill them.

The statement, "There are regions beneath Earth's crust that will always be beyond the reach of scientific investigation" is A) scientific statement B) a fact C) a hypothesis D) a theory E) speculation

e) speculation

If a freely falling object were to somehow equipped with a speedometer, its speed reading would increase each second by Select one: a. 15 m/s. b. depends on the initial speed. c. a variable amount d. 5 m/s. e. 10 m/s.

e. 10 m/s Acceleration due to gravity is -10m/s2 which means the speed changes by 10 m/s every second.

An object falls freely from rest on a planet where the acceleration due to gravity is 20 m/s2. After 5 seconds, the object will have a speed of Select one: a. 5 m/s. b. 10 m/s. c. 20 m/s. d. 50 m/s. e. 100 m/s.

e. 100 m/s v = Vo + at v = 0 + (20)(5 v = 100 m/s