PHYS-1305-027 Chapter's 2 & 3

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) 0. B) 5. C) 8. D) 24

A - 0

If a projectile is fired straight up at a speed of 10 m/s, the time it takes to reach the top of its path is about A) 1 second. B) 2 seconds. C) 10 seconds. D) not enough information to estimate

A - 1 second.

At one instant a heavy object in air is moving upward at 50 meters per second. One second later its speed is approximately A) 40 m/s. B) 50 m/s. C) 55 m/s. D) 60 m/s.

A - 40 m/s.

A pot falls from a ledge and hits the ground 45 m below. The speed with which it hits the ground is (Hint: use the formula for "t", then use the result in the formula for "v") A) about 30 m/s. B) about 60 m/s. C) about 120 m/s. D) more than 120 m/s.

A - about 30 m/s.

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 50 m/s B) about 60 m/s C) about 80 m/s D) about 100 m/s E) about 110 m/s

A - about 50 m/s

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 below. The rock hits the floor A) exactly below the midpoint of the ceiling. B) ahead of the midpoint of the ceiling. C) behind the midpoint of the ceiling. D) More information is needed to solve this problem. E) none of these.

A - exactly below the midpoint of the ceiling

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) inertia. B) gravity. C) acceleration. D) resistance.

A - inertia

While an object near the Earth's surface is in free fall, its A) velocity increases. B) acceleration increases. C) mass increases. D) mass decreases

A - velocity increases.

A car maintains a constant velocity of 100 km/hr for 10 seconds. During this interval its acceleration is A) zero. B) 10 km/hr. C) 110 km/hr. D) 1000 km/hr.

A - zero.

An apple falls from a tree and hits the ground 5 meters below. It hits the ground with a speed of about (Hint: use the formula for "t", then use the result in the formula for "v") A) 5 m/s. B) 10 m/s. C) 15 m/s. D) 20 m/s. E) not enough information given to estimate

B - 10 m/s.

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 its initial speed

B - 10 m/s.

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 30 m/s? A) 2 seconds B) 15 seconds C) 30 seconds D) 60 seconds E) none of these

B - 15 seconds

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) 1 second. B) 2 seconds. C) 10 seconds. D) 20 seconds. E) not enough information to estimate

B - 2 seconds.

A horse gallops a distance of 10 kilometers in a time of 30 minutes. Its average speed is A) 15 km/h. B) 20 km/h. C) 30 km/h. D) 40 km/h.

B - 20 km/h.

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 A) 10 m/s. B) 20 m/s. C) 30 m/s. D) 40 m/s. E) depends on its initial speed

B - 20 m/s.

A man leans over the edge of a cliff and throws a rock upward at 4.9 m/s. Neglecting air resistance, one second later the rock's speed is A) zero. B) 4.9 m/s. C) 9.8 m/s. D) 14.7 m/s. E) none of the above

B - 4.9 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 A) 200 N. B) 400 N. C) 800 N. D) none of these.

B - 400 N

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 A) less than 9.8 meters per second per second. B) 9.8 meters per second per second. C) greater than 9.8 meters per second per second

B - 9.8 meters per second per second,

The scientist to first introduce the concept of inertia was A) Aristotle. B) Galileo. C) Newton. D) Copernicus

B - Galileo

A ball is thrown 125 meters upward and then falls the same distance back to Earth. Neglecting air resistance, its total time in the air is A) about 5 seconds. B) about 10 seconds. C) about 15 seconds. D) more than 20 seconds.

B - about 10 seconds.

If an object moves with constant acceleration, its velocity must A) be constant also. B) change by the same amount each second. C) change by varying amounts depending on its speed. D) always decrease.

B - change by the same amount each second.

If no external forces (ΣF = 0) are acting on a moving object, it will A) continue moving at the same speed. B) continue moving at the same velocity. C) move slower and slower until it finally stops.

B - continue moving at the same velocity.

Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the tendency of the rock is to A) continue to follow a circular path. B) follow a straight-line path. C) increase its speed. D) revolve in a smaller circle.

B - follow a straight-line path

A bullet is fired straight down from the top of a high cliff. Neglecting air resistance, the acceleration of the bullet in meters per second per second A) is less than 9.8. B) is 9.8. C) is more than 9.8. D) depends on the height of the cliff.

B - is 9.8

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) more than the speed it had when thrown upwards. B) less than the speed it had when thrown upwards. C) the same as the speed it had when thrown upwards. D) impossible to determine.

B - less than the speed it had when thrown upwards

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 A) half as much. B) the same amount. C) twice as much. D) four times as much

B - the same amount.

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 A) half as much. B) the same. C) twice as much. D) four times as much.

B - the same.

A sheet of paper can be withdrawn from under a container of milk without toppling it if the paper is jerked quickly. This best demonstrates that A) the milk carton has no acceleration. B) there is an action-reaction pair of forces. C) gravity tends to hold the milk carton secure. D) the milk carton has inertia. E) none of these

B - there is an action-reaction pair of forces

Galileo's interpretation of motion differed from Aristotle's in that Galileo emphasized A) the acceleration of free fall. B) time rates. C) the role of distance in describing motion. D) all of these. E) none of these.

B - time rates

When a rock thrown straight upwards gets to the exact top of its path, its A) velocity is zero and its acceleration is zero. B) velocity is zero and its acceleration is about 10 meters per second per second. C) velocity is about 10 m/s and its acceleration is zero. D) velocity is about 10 m/s and its acceleration is about 10 meters per second per second. E) none of these

B - velocity is zero and its acceleration is about 10 meters per second per second.

Ten seconds after starting from rest, a car is moving at 40 m/s. What is the car's acceleration in meters per second per second? A) 0.25 B) 2.8 C) 4.0 D) 10 E) 40

C

The force of friction on a sliding object is 10 N. The applied force needed to maintain a constant velocity is A) more than 10 N. B) less than 10 N. C) 10 N.

C - 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? A) 5 m/s B) 7.5 m/s C) 10 m/s D) 15 m/s E) 20 m/s

C - 10 m/s.

A 300-kg (mass) bear grasping a vertical tree slides down at constant velocity. The friction force between the tree and the bear is A) 30 N. B) 300 N. C) 3000 N. D) more than 3000 N.

C - 3000 N

If a rocket initially at rest accelerates at a rate of 50 m/s2 for one minute, its speed will be A) 50 m/s. B) 500 m/s. C) 3000 m/s. D) 3600 m/s

C - 3000 m/s.

One half second after starting from rest, a freely falling object will have a speed of about A) 20 m/s. B) 10 m/s. C) 5 m/s. D) 2.5 m/s. E) none of these.

C - 5 m/s.

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 - about 180 m

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) zero. B) less than 30 m/s but larger than zero. C) about 30 m/s. D) more than 30 m/s. E) More information is needed for an estimate.

C - about 30 m/s.

Disregarding air resistance, objects fall with constant A) velocity. B) speed. C) acceleration. D) distances each successive second

C - acceleration.

Hang from a pair of gym rings and the upward support forces of the rings will always A) each be half your weight. B) each equal your weight. C) add up to equal your weight

C - add up to equal your weight

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 fired bullet is greater. B) the dropped bullet is greater. C) each bullet is 9.8 meters per second per second

C - each bullet is 9.8 meters per second per second.

Whereas Aristotle relied on logic in explaining nature, Galileo relied on A) logic also. B) patterns. C) experiment. D) mathematics

C - experiment

A bullet is dropped into a river from a very high bridge. At the same time, another bullet is fired from a gun, straight down towards the water. Neglecting air resistance, the acceleration just before striking the water A) is greater for the dropped bullet. B) is greater for the fired bullet. C) is the same for each bullet. D) depends on how high they started. E) none of these.

C - is the same for each bullet

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 the greater speed will be A) the one thrown upward. B) the one thrown downward. C) neither -- they will both hit with the same speed.

C - neither -- they will both hit with the same speed.

When a rocket ship accelerating in outer space runs out of fuel, it A) accelerates for a short time, then slows down to a constant velocity. B) accelerates for a short time, slows down, and eventually stops. C) no longer accelerates

C - no longer accelerates

A car accelerates at 2 meters/s/s. Assuming the car starts from rest, how far will it travel in 10 s? A) 2 m B) 10 m C) 40 m D) 100 m E) 200 m

D - 100 m

A man leans over the edge of a cliff and throws a rock upward at 4.9 m/s. Neglecting air resistance, two seconds later the rock's speed is A) zero. B) 4.9 m/s. C) 9.8 m/s. D) 14.7 m/s. E) none of the above.

D - 14.7 m/s.

If a car accelerates from rest at 2 meters per second per second, its speed 3 seconds later will be about A) 2 m/s. B) 3 m/s. C) 4 m/s. D) 6 m/s

D - 6 m/s.

At one instant an object in free fall is moving downward at 50 meters per second. One second later its speed should be about A) 25 m/s. B) 50 m/s. C) 55 m/s. D) 60 m/s. E) 100 m/s.

D - 60 m/s.

An object in mechanical equilibrium is an object A) at rest. B) moving with constant velocity. C) having no acceleration. D) all of these.

D - all of these.

According to Newton's law of inertia, a railroad train in motion should continue going forever even if its engine is turned off. We never observe this because railroad trains A) move too slowly. B) are much too heavy. C) must go up and down hills. D) always have forces that oppose their motion.

D - always have forces that oppose their motion.

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) in the direction of motion. B) opposite its velocity. C) directed upward. D) directed downward

D - directed upward.

While a car travels around a circular track at a constant speed, its A) acceleration is zero. B) velocity is zero. C) inertia is zero. D) none of the above

D - inertia is zero.

Twelve seconds after starting from rest, an object falling freely will have a speed of A) 10 m/s. B) 50 m/s. C) 100 m/s. D) more than 100 m/s.

D - more than 100 m/s.

Starting from rest, the distance a freely falling object will fall in 0.5 second is about A) 1 m. B) 10 m. C) 1.00 m. D) none of the above.

D - none of the above