Physics 100 - Week 2: Knowledge Check

Phil leans over the edge of a cliff and throws a rock upward at 5 m/s. Neglecting air resistance, two seconds later the rock's speed is a. None of these b. 15 m/s. c. 5 m/s. d. zero. e. 10 m/s.

b. 15 m/s.

A ball starting from rest at the top of an inclined plane gains a speed of 2 m/s for each second it rolls. What is its acceleration down the incline? a. 4 m/s2 b. 2 m/s2 c. 1 m/s2 d. 0.5 m/s2

b. 2 m/s2

The total time it takes a projectile fired straight up at 10 m/s to reach the top of its path and return to its starting point is about a. 10 s. b. 2 s. c. 20 s. d. 1 s.

b. 2 s.

When you walk at an average speed of 4 m/s, in 5 s you'll cover a distance of a. 10 m. b. 20 m. c. 2 m. d. 15 m.

b. 20 m.

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 a. 10 m/s. b. 20 m/s. c. 30 m/s. d. 40 m/s.

b. 20 m/s.

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

b. 40 m/s.

An 80-km/h airplane flying in the same direction as a 10 km/h tail wind has a groundspeed of a. 80 km/h. b. 90 km/h. c. 10 km/h. d. 70 km/h.

b. 90 km/h.

While a car travels around a circular track at a constant speed, its a. velocity is zero. b. None of these c. acceleration is zero. d. inertia is zero.

b. None of these

A seagull flying at 10 km/h in a 10-km/h crosswind has a resultant speed of a. 10 km/h. b. about 14 km/h. c. 20 km/h. d. more than 20 km/h.

b. about 14 km/h.

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 is a. 0 m/s2. b. 8 m/s2. c. 24 m/s2. d. 5 m/s2.

a. 0 m/s2.

The time it takes a projectile fired straight up at 10 m/s to reach the top of its path is about a. 1 s. b. 10 s. c. 2 s. d. not enough information

a. 1 s.

A bird flying at 8 km/h in a 6-km/h crosswind has a resultant speed of a. 10 km/h. b. 6 km/h. c. 14 km/h. d. 8 km/h.

a. 10 km/h.

A motorboat that normally travels at 8 km/h in still water heads directly across a 6-km/h flowing river. The resulting speed of the boat is about a. 10 km/h. b. 6 km/h. c. 20 km/h. d. 8 km/h.

a. 10 km/h.

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

a. 10 m/s.

If you throw a ball straight downward (in the absence of air resistance), after leaving your hand its acceleration is a. 10 m/s2. b. greater than 10 m/s2. c. less than 10 m/s2.

a. 10 m/s2.

When a ball thrown straight upwards reaches the very top of its path, its acceleration is a. 10 m/s2. b. 5 m/s2. c. None of these d. zero.

a. 10 m/s2.

An airplane that flies at 100 km/h in a 100-km/h crosswind has a ground speed of a. 141 km/h. b. 0 km/h. c. 100 km/h. d. 200 km/h.

a. 141 km/h.

The average speed of a horse that gallops 10 kilometers in 30 minutes is a. 20 km/h. b. 30 km/h. c. 40 km/h. d. 15 km/h.

a. 20 km/h.

If a freely falling object were equipped with a speedometer on a planet where the acceleration due to gravity is 20 m/s2, then its speed reading would increase each second by a. 20 m/s. b. 40 m/s. c. 30 m/s. d. 10 m/s. e. depends on its initial speed

a. 20 m/s.

Neglecting air resistance, how fast must you toss a ball straight up in order for it to take 6 seconds to return to its initial level? a. 30 m/s b. 5 m/s c. 10 m/s d. more than 30 m/s e. 20 m/s

a. 30 m/s

A humming bird flying at 4 km/h that gets caught in a 3-km/h crosswind has a resultant speed of about a. 5 km/h. b. 4 km/h. c. more than 5 km/h. d. 3 km/h.

a. 5 km/h.

A car's speed 3 seconds after accelerating from rest at 2 m/s2 is a. 6 m/s. b. 2 m/s. c. 4 m/s. d. 3 m/s.

a. 6 m/s.

If an object moves with constant acceleration, its velocity must a. change by the same amount each second. b. always decrease. c. change by varying amounts depending on its speed. d. be constant also.

a. change by the same amount each second.

Katelyn runs along the aisle of a train that moves at 8 m/s. Her speed relative to the floor is 3 m/s. Her speed relative to an observer at rest on the ground is a. either depending on her running direction b. None of these c. 5 m/s. d. 11 m/s.

a. either depending on her running direction

As water drops fall at a steady rate from a leaking faucet they a. get farther apart. b. remain at a relatively fixed distance from one another. c. get closer together.

a. get farther apart.

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

a. greater than the second before.

A ball rolls along a horizontal track in a certain time. If the track has a dip in it, the time to roll the length of the track will be Select one: a. less. b. the same. c. more.

a. less.

The accelerations possible for a ball on an inclined plane a. range from zero to g. b. have no limit. c. range from g to infinity.

a. range from zero to g.

A bullet is dropped into a river from a very high bridge at the same time as another bullet is fired straight downward from a rifle. Neglecting air resistance, the acceleration just before striking the water is a. the same for each bullet. b. None of these c. greater for the dropped bullet. d. greater for the fired bullet.

a. the same for each bullet.

A cart maintains a constant velocity of 100 m/s for 10 seconds. During this interval its acceleration is a. zero. b. 10 m/s2. c. 1 m/s2. d. None of these

a. zero.

The muzzle velocity of a bullet fired from a new rifle is 100 m/s. Neglecting air resistance, at the end of one second a bullet fired straight up into the air will have traveled a distance of a. None of these b. (100 - 5) m. c. (100 + 5) m. d. 100 m. e. 5 m.

b. (100 - 5) m.

A mosquito flying at 3 m/s that encounters a breeze blowing at 3 m/s in the opposite direction has a speed of a. 4 m/s. b. 0 m/s. c. 6 m/s. d. 3 m/s.

b. 0 m/s.

A cart changes its speed from 90 m/s to 100 m/s in 10 seconds. During this interval its acceleration is a. 10 m/s2. b. 1 m/s2. c. None of these d. zero.

b. 1 m/s2.

The vertical height attained by a basketball player who achieves a hang time of a full 1 s is about a. 2.5 m. b. 1.2 m. c. 1 m. d. 0.8 m. e. more than 2.5 m.

b. 1.2 m.

A ball is projected 125 meters straight upward and then falls the same distance back to its starting point. Neglecting air resistance, its total time in the air is about a. 5 s. b. 10 s. c. 15 s. d. more than 20 s.

b. 10 s.

You're at rest in a hammock when a hungry mosquito sees an opportunity for lunch. A mild 2-m/s breeze is blowing. If the mosquito joins you for lunch it should hover over you by flying a. with the breeze at 2 m/s. b. against the breeze at 2 m/s. c. a bit faster than wind speed. d. None of these

b. against the breeze at 2 m/s.

Compared with hang time on Earth, hang time on the Moon would be a. the same. b. greater. c. less.

b. greater.

The distance a freely falling bowling ball falls each second a. is about 10 m. b. increases. c. is about 5 m. d. None of these

b. increases.

The speedometer of an automobile reads a. accelerated speed. b. instantaneous speed. c. average speed.

b. instantaneous speed.

Which of the following is not a vector quantity? a. velocity b. speed c. acceleration d. none are vector quantities. e. all are vector quantities

b. speed

While an iron block near the Earth's surface is in free fall, it undergoes an increase in a. neither of these b. speed. c. both of these d. acceleration.

b. speed.

A rock dropped from a 5-m height accelerates at 10 m/s2 and strikes the ground 1 s later. If the rock is dropped from a height of 2.5 m, its acceleration of fall is a. half. b. the same. c. four times as much. d. twice.

b. the same.

Phil leans over the edge of a cliff and throws a rock upward at 5 m/s. How far below the level from which it was thrown is the rock 2 seconds later? Select one: a. 15 m b. 20 m c. 10 m d. 5 m

c. 10 m

Jogging Jake runs at 4 m/s along a train flatcar that moves at 10 m/s in the same direction. Jake's speed relative to the ground is a. None of these b. 10 m/s. c. 14 m/s. d. 6 m/s.

c. 14 m/s.

If a stone falls to the bottom of a mineshaft in 6 seconds, then the depth of the shaft is about a. 60 m. b. more than 200 m. c. 180 m. d. 120 m.

c. 180 m.

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 a. 500 m. b. 150 m. c. 250 m. d. None of these e. 100 m.

c. 250 m.

A pot that falls from a ledge and hits the ground 45 m below hits the ground at a. more than 120 m/s. b. 120 m/s. c. 30 m/s. d. 60 m/s.

c. 30 m/s.

Ten seconds after starting from rest, a car is moving at 40 m/s. What is the car's acceleration? a. 0.25 m/s2 b. 2.8 m/s2 c. 4.0 m/s2 d. 40 m/s2 e. 10 m/s2

c. 4.0 m/s2

A mosquito flying at 3 m/s that encounters a breeze blowing at 3 m/s in the same direction has a speed of a. 3 m/s. b. 4 m/s. c. 6 m/s. d. 0 m/s.

c. 6 m/s.

Jogging Jake runs at 4 m/s along a train flatcar that moves at 10 m/s in the opposite direction. Jake's speed relative to the ground is a. 10 m/s. b. 14 m/s. c. 6 m/s. d. None of these

c. 6 m/s.

At one instant an object in free fall is moving downward at 50 m/s. One second later its speed is a. 100 m/s. b. 25 m/s. c. 60 m/s. d. 55 m/s. e. 50 m/s.

c. 60 m/s.

A ball starting from rest at the top of an inclined plane accelerates at 2 m/s2 and reaches the bottom of the plane in 3 seconds. What is the length of the plane? a. 3 m b. 2 m c. 9 m d. 5 m

c. 9 m

A freely-falling watermelon falls with constant a. distances each successive second. b. velocity. c. acceleration. d. speed.

c. acceleration.

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

c. distance and time.

Twelve seconds after starting from rest, a freely-falling cantelope has a speed of a. 50 m/s. b. 100 m/s. c. more than 100 m/s. d. 10 m/s.

c. more than 100 m/s.

A ball rolls along a horizontal track in a certain time. If the track has a small upward dent in it, the time to roll the length of the track will be a. less. b. the same. c. more.

c. more.

Phil Physiker standing at the edge of a cliff throws one ball straight up and another ball straight down, both with the same speed. Neglecting air resistance, which ball hits the ground below with the greater speed? a. the one thrown downward b. the one thrown upward c. neither, both hit with the same speed

c. neither, both hit with the same speed

Neglecting air resistance, a bullet fired straight down from the top of a high cliff has an acceleration of a. more than 10 m/s2. b. less than 10 m/s2. c. depends on the height of the cliff. d. 10 m/s2.

d. 10 m/s2.

An 80-km/h airplane caught in a 60-km/h crosswind has a resultant speed of a. 141 km/h. b. 80 km/h. c. 60 km/h. d. 100 km/h.

d. 100 km/h.

A river 100 m wide flows due south at 1 m/s. A boat that travels 1 m/s relative to the water is pointed due east as it crosses from the west bank. The boat reaches the east bank a. due east of its starting point. b. 141 m farther south. c. None of these d. 100 m farther south.

d. 100 m farther south.

A river 100 m wide flows 1 m/s due south. A boat that travels 1 m/s relative to the water is pointed due east as it crosses from the west bank. Relative to its starting point, the boat travels a. more than 200 m. b. 200 m. c. nowhere. d. 141 m. e. 100 m.

d. 141 m.

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. 3600 m/s. d. 3000 m/s.

d. 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. None of these c. 10 m/s. d. 5 m/s. e. 2 m/s.

d. 5 m/s.

Phil leans over the edge of a cliff and throws a rock upward at 5 m/s. Neglecting air resistance, one second later the rock's speed is a. 15 m/s. b. 10 m/s. c. zero. d. 5 m/s. e. None of these

d. 5 m/s.

Neglecting air resistance, a ball projected straight upward so it remains in the air for 10 seconds needs an initial speed of a. 60 m/s. b. 110 m/s. c. 100 m/s. d. 50 m/s. e. 80 m/s.

d. 50 m/s.

If a car increases its velocity from zero to 60 m/s in 10 seconds, its acceleration is a. 60 m/s2. b. 3 m/s2. c. 600 m/s2. d. 6 m/s2.

d. 6 m/s2.

An 80-km/h airplane flying against a 10-km/h head wind has a groundspeed of a. 80 km/h. b. 90 km/h. c. 10 km/h. d. 70 km/h.

d. 70 km/h.

A vehicle undergoes acceleration when it a. changes its direction. b. loses speed. c. gains speed. d. All of these

d. All of these

The distance a freely falling object falls from rest in one-half second is a. 6 m. b. 2 m. c. 4 m. d. None of these

d. None of these

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. directed upward. c. None of these d. directed downward. e. opposite its velocity.

d. directed downward.

A ball is thrown upwards and returns to the same location. Compared with its initial speed its speed when it returns is about a. four times as much. b. twice as much. c. half as much. d. the same.

d. the same.

An apple falls from a tree and hits the ground 5 meters below with a speed of about a. 15 m/s. b. 20 m/s. c. 5 m/s. d. not enough information e. 10 m/s.

e. 10 m/s.

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 a. 20 m/s. b. 5 m/s. c. 50 m/s. d. 10 m/s. e. 100 m/s.

e. 100 m/s.

The time it takes a car to attain a speed of 30 m/s when accelerating from rest at 2 m/s2 is a. 30 s. b. 2 s. c. None of these d. 60 s. e. 15 s.

e. 15 s.

What is the acceleration of a car that starts from rest and 5 seconds later reaches a speed of 20 m/s? a. 3 m/s2 b. 5 m/s2 c. 1 m/s2 d. 2 m/s2 e. 4 m/s2

e. 4 m/s2