Test #1 Review

A rocket becomes progressively easier to accelerate as it travels upward from the ground mainly because: a. the mass of the rocket decreases as fuel is burned b. the applied force on the rocket increases as burning of fuel progresses c. gravity becomes weaker with increased distance

a. the mass of the rocket decreases as fuel is burned

A force of 1 N accelerates a mass of 1 kg at the rate of 1 m/s/s. The acceleration of a mass of 2 kg acted upon by a net force of 2 N is: a. the same b. half as much c. twice as much d. none of these

a. the same

When a falling object has reached its terminal velocity, its acceleration is: a. zero b. constant c. g

a. zero

A car maintains a constant velocity of 100 km/h for 10 seconds. During this interval, it's acceleration is: a. zero b. 1000 km/h c. 110 km/h d. 10 km/h

a. zero (if velocity is constant, acceleration is zero)

A package falls off a truck that is moving at 30 m/s. Neglecting air resistance, the horizontal speed of the package just before it hits the ground is: a. more than 30 m/s b. about 30 m/s c. zero d. less than 30 m/s, but larger than zero e. more information is needed for an estimate

b. about 30 m/s

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: a. the dropped bullet is greater b. each bullet is 10 m/s/s c. the fired bullet is greater

b. each bullet is 10 m/s/s

The newton is a unit of: a. inertia b. force c. density d. mass

b. 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: a. doubled b. greater than the second before c. less and less each second d. constant

b. greater than the second before

If an object's mass is decreasing while a constant force is applied to the object, the acceleration: a. remains the same b. increases c. decreases

b. increases

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: a. 5 b. 8 c. 0 d. 24

c. 0 (constant velocity=zero acceleration; velocity is 8 m/s each time, so constant)

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. 180 m (d=1/2g times t squared; d= .5 x 10 x 6 squared; d= 5 x 6 squared; d= 5 x 36= 180)

The gain in speed each second for a freely-falling object is about: a. 0 b. 5 m/s c. 20 m/s d. 10 m/s e. depends on initial speed

d. 10 m/s

A car accelerates from rest for 5 seconds until it reaches a speed of 20 m/s. What is the car's acceleration in meters per second per second?: a. 1 b. 2 c. 3 d. 4 e. 5

d. 4 m/s/s (a=change in speed divided by time interval; a= 20 divided by 5= 4 m/s/s)

At one instant, a heavy object in air is moving upward at 50 m/s. One second later, its speed in m/s is approximately: a. 55 m/s b. 50 m/s c. 60 m/s d. 40 m/s

d. 40 m/s (object already in air at 50 m/s; speed slows down going upward, increases going down)

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

d. 6 km/h/s (60 divided by 10; because a= change in speed/time interval, along a straight line)

Compared to a 1-kg block of solid iron, a 2-kg block of solid iron has twice as much: a. volume b. inertia c. mass d. all of these e. none of these

d. all of these

An object maintains a constant acceleration unless there is a change in: a. its mass b. the air resistance c. the applied force d. any of the above

d. any of the above

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: a. friction of the ground against the archer's feet b. grip of the archer's hand on the bow c. air resistance against the bow d. arrow's push against the bowstring e. combined weight of the arrow and bowstring

d. arrow's push against the bowstring

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: a. acceleration b. resistance c. gravity d. inertia

d. inertia (property in things to resist change in motion)

While a car travels around a circular track at a constant speed, its: a. inertia is zero b. velocity is zero c. acceleration is zero d. none of the above

d. none of the above (inertia is related to mass, so has to weigh something; velocity is changing because direction is changing to follow circular path-no mention of returning to original point-; always accelerating towards the center of the circular path)

A 10-kg brick and a 1-kg book are dropped in a vacuum. The force of gravity on the 10-kg brick is: a. 10 times as much b. zero c. one-tenth as much d. the same as the force on the 1-kg book

a. 10 times as much (mass is 10 times greater; dealing with force of gravity)

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: a. 2 seconds b. 1 second c. 10 seconds d. 20 seconds e. not enough information to estimate

a. 2 seconds (1 second up, 1 second down)

If a car accelerates from rest at 2 m/s/s, its speed 3 seconds later will be about: a. 6 m/s b. 4 m/s c. 2 m/s d. 3 m/s

a. 6 m/s (2 m/s/s times 3 s; two of the second units cancel each other, so converts to just m/s)

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: a. directed downward b. opposite its velocity c. directed upward d. in the direction of motion

a. directed downward (gravity causes acceleration downward; attracted to Earth, trying to get back to it in a hurry)

Whirl a rock at the end of a string on an ice-covered pond and it follows a circular path. If the string breaks, the tendency of the rock is to: a. follow a straight-line path b. continue to follow a circular path

a. follow a straight-line path (the string is what causes it to follow a circular path)

When you relax at rest with your left foot on one bathroom scale and your right foot on a similar scale, each of the scales will: a. indicate different values that will equal your weight when added together b. indicated exactly half your weight c. indicate part of your total weight, but not necessarily half of it d. any of the above may be correct

a. indicate different values that will equal your weight when added together

The last instant just before an airplane crashes, a passenger jumps out the door and falls only 2 feet to the ground. The passenger is: a. probably hurt or killed b. intelligent to think so fast c. unharmed d. lucky to have studied physics

a. probably hurt or killed

Two factors that greatly affect air resistance on falling objects are the: a. size and speed of the object b. size and weight of the object c. size and mass of the object

a. size and speed of the object

Galileo's use of inclined planes allowed him to effectively: a. slow down the acceleration of free fall b. eliminate the acceleration of free fall c. increase the acceleration beyond that of free fall d. eliminate friction

a. slow down the acceleration of free fall (lacked accurate timing devices to measure falling objects)

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: a. the mass of the car is independent of gravity b. the weight of the car is independent of gravity c. nonsense! A car is much more easily accelerated on the moon than on the Earth

a. the mass of the car is independent of gravity (mass of an object is the same no matter where it is)

An apple weighs 1 N. When held at rest above your head, the net force on the apple is: a. 1 N b. 0 N c. 9.8 N d. 0.1 N e. none of these

b. 0 N (state of equilibrium, at rest, zero force)

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?: a. 3000 kg b. 1500 kg c. 1000 kg d. 500 kg e. none of these

b. 1500 kg (mass= force divided by acceleration due to force= mass times acceleration formula; mass= 3000 divided by 2= 1500 kg)

Two people, one twice as massive as the other, attempt a tug-of-war with 12 m of massless rope on frictionless ice. After a brief time, they meet. The heavier person slides a distance of: a. 0 m b. 4 m c. 3 m d. 6 m

b. 4 m (12 divided by 3= 4)

If a non-rotating object has no acceleration, then we can say for certain that it is: a. moving at constant non-zero velocity b. in mechanical equilibrium c. at rest d. all of these e. none of these

b. in mechanical equilibrium (mechanical covers static and dynamic types of equilibrium; we do not know for certain if the object is static or dynamic, but we do know for certain it's in equilibrium)

A ball is thrown upwards and caught when it comes back down. In the presence of air resistance, the speed with which it is caught is always: a. the same as the speed it had when thrown upwards b. less than the speed it had when thrown upwards c. more than the speed it had when thrown upwards d. impossible to determine

b. less than the speed it had when thrown upwards (if neglecting air resistance, would be the same speed)

In which case would you have the largest mass of gold? If your chunk of gold weighed 1 N on the: a. Earth b. moon c. planet Jupiter

b. moon (less gravity, so have to have larger mass to generate the same force on planets)

As an object freely falls downward, its: a. acceleration increases b. velocity increases c. both of these d. none of these

b. velocity increases (acceleration in free fall is constant)

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: a. equal to its weight b. zero c. equal to the product of its mass times its weight d. equal to its weight divided by its mass

b. zero (force only necessary to stop it or change it's direction)

An object released from rest on another planet requires 1 second to fall a distance of 6 meters. What is the acceleration in m/s/s due to gravity on this planet?: a. 3 b. 15 c. 12 d. 6 e. none of these

c. 12 (use distance formula to find acceleration because you have distance and time and need to find acceleration, so substitute a for g; d=1/2 times acceleration times time squared; 6= 1/2 times a times 1 squared; work formula to get a on one side; a= 6 divided by 1/2 times 1 squared= 12)

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 m/s/s when taking off?: a. 4 b. 1 c. 2 d. 0.25 e. none of these

c. 2 (force=mass times acceleration; change to acceleration= force divided by mass; a= 50,000(4) divided by 100,000= 200,000 divided by 100,000= 2)

A ride on a roller-coaster car containing 6 passengers takes 3 minutes. Neglecting friction, a similar ride with 12 passengers aboard would take: a. 1.5 minutes b. 6 minutes c. 3 minutes d. 18 minutes

c. 3 minutes (the same amount of time, mass has no effect)

A 10-N falling object encounters 4 N of air resistance. The net force on the object is: a. 0 N b. 10 N c. 6 N d. 4 N e. none of these

c. 6 N (net force= mass - resistance; net force= 10-4= 6 N)

A heavy block at rest is suspended by a vertical rope. When the block is accelerated upward by the rope, the rope tension: a. remains the same b. decreases c. increases

c. increases (tension has to increase to pull block upward)

Which of the following is not a vector quantity?: a. acceleration b. velocity c. speed d. all are vector quantities

c. speed (vector quantities have magnitude and direction; speed is a scalar quantity)

A car traveling at 100 km/h strikes an unfortunate bug and splatters it. The force of impact is: a. greater on the bug b. greater on the car c. the same for both

c. the same for both (impact is the same force, but damage is different because mass is different)

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

d. increasing (distance of free fall will increase with time)

A feather and a coin will have equal accelerations when falling in a vacuum because: a. the force of gravity is the same for each in a vacuum b. their velocities are the same c. the force of gravity does not act in a vacuum d. the ratio of each object's weight to its mass is the same e. none of these

d. the ratio of each object's weight to its mass is the same

A ball is thrown upwards. Neglecting air resistance, what initial upward speed does the ball need to remain in the air for a total time of 10 seconds? a. about 80 m/s b. about 110 m/s c. about 100 m/s d. about 60 m/s e. about 50 m/s

e. about 50 m/s (5 seconds up & 5 seconds down; t divided by 2 times 10 m/s; 10 seconds divided by 2 times 10 m/s= 5 s times 10 m/s= 50 m/s)

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?: a. the attraction to the planets, stars, and every particle in the universe b. water resistance that will soon act upward on the diver c. air resistance the diver encounters while falling d. all of these e. none of these

e. none of these (the reaction is the push of the diver against the Earth)

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: a. 2 times as far b. 1/2 as far c. 4 times as far d. 1-1/2 times as far e. the same

e. the same