ch3 physics

An airplane that flies at 100 km/h in a 100-km/h crosswind has a ground speed of

0km/h

Phil leans over the edge of a cliff and throws a rock upward at 5 m/s. How far below the level from 10) which it was thrown is the rock 2 seconds later?

10 m

If you throw a ball straight downward (in the absence of air resistance), after leaving your hand its 3) acceleration is

10 m/s2

Neglecting air resistance, a bullet fired straight down from the top of a high cliff has an acceleration 4) of

10 m/s2.

A ball is projected 125 meters straight upward and then falls the same distance back to its starting 13) point. Neglecting air resistance, its total time in the air is about

10 s

An 80-km/h airplane caught in a 60-km/h crosswind has a resultant speed of

100km/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 16) pointed due east as it crosses from the west bank. The boat reaches the east bank

100m farther south

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

100m/s

A motorboat that normally travels at 8 km/h in still water heads directly across a 6-km/h flowing 14) river. The resulting speed of the boat is about

10km/h

One half second after starting from rest, a freely falling object will have a speed of about

10m/s

When a ball thrown straight upwards reaches the very top of its path, its acceleration is

10m/s2

A river 100 m wide flows 1 m/s due south. A boat that travels 1 m/s relative to the water is pointed 5) due east as it crosses from the west bank. Relative to its starting point, the boat travels

141 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

14m/s

The time it takes a car to attain a speed of 30 m/s when accelerating from rest at 2 m/s2 is

15s

if a stone falls to the bottom of a mineshaft in 6 seconds, then the depth of the shaft is about

180m

A cart changes its speed from 90 m/s to 100 m/s in 10 seconds. During this interval its acceleration 43) is

1m/s2

If a freely falling object were equipped with a speedometer on a planet where the acceleration due 2) to gravity is 20 m/s2, then its speed reading would increase each second by

20 m/s

The average speed of a horse that gallops 10 kilometers in 30 minutes is

20km/h

When you walk at an average speed of 4 m/s, in 5 s you'll cover a distance of

20m

An object falls freely from rest on a planet where the acceleration due to gravity is twice as much as 6) on Earth. In the first 5 seconds it falls a distance of

250 m

A ball starting from rest at the top of an inclined plane gains a speed of 2 m/s for each second it 46) rolls. What is its acceleration down the incline?

2m/s2

If a rocket initially at rest accelerates at a rate of 50 m/s2 for one minute, its speed will be

3000m/s

A pot that falls from a ledge and hits the ground 45 m below hits the ground at

30m/s

Ten seconds after starting from rest, a car is moving at 40 m/s. What is the car's acceleration?

4 m/s2

At one instant a heavy object in air is moving upward at 50 m/s. One second later its speed is 38) approximately

40m/s

Neglecting air resistance, a ball projected straight upward so it remains in the air for 10 seconds 29) needs an initial speed of

50 m/s

A humming bird flying at 4 km/h that gets caught in a 3-km/h crosswind has a resultant speed of 34) about

5km/h

If a freely falling object were equipped with a speedometer, its speed reading would increase each second by about

5m/s

If a car increases its velocity from zero to 60 m/s in 10 seconds, its acceleration is

6 m/s2

At one instant an object in free fall is moving downward at 50 m/s. One second later its speed is

60m/s

An 80-km/h airplane flying against a 10-km/h head wind has a groundspeed of

70km/h

A ball starting from rest at the top of an inclined plane accelerates at 2 m/s2 and reaches the bottom 19) of the plane in 3 seconds. What is the length of the plane?

9m

The distance a freely falling object falls from rest in one-half second is A) 4 m. B) 6 m. C) 2 m. D) none of the above

D

GRAVITY / FREE FALL =

acceleration = -10m/s2

You're at rest in a hammock when a hungry mosquito sees an opportunity for lunch. A mild 2-m/s 25) breeze is blowing. If the mosquito joins you for lunch it should hover over you by flying A) against the breeze at 2 m/s. B) a bit faster than wind speed. C) with the breeze at 2 m/s. D) none of the above

against breeze at 2m/s

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

b get farther apart

Phil Physiker standing at the edge of a cliff throws one ball straight up and another ball straight 17) down, both with the same speed. Neglecting air resistance, which ball hits the ground below with the greater speed? A) the one thrown upward B) the one thrown downward C) neither, both hit with the same speed

c. neither

If an object moves with constant acceleration, its velocity must

change by the same amount each second

The two measurements necessary for calculating average speed are

distance and time

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

either depending on her running direction

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

greater than the second before.

The distance a freely falling bowling ball falls each second

increases

The speedometer of an automobile reads A) instantaneous speed. B) accelerated speed. C) average speed.

instantaneous speed

Twelve seconds after starting from rest, a freely-falling cantelope has a speed of

more than 100m/s

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

none of the above

The accelerations possible for a ball on an inclined plane A) range from g to infinity. B) have no limit. C) range from zero to g.

range from 0 to g

While an iron block near the Earth's surface is in free fall, it undergoes an increase in

speed

A ball is thrown upwards and returns to the same location. Compared with its initial speed its 12) speed when it returns is about

the same

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

the same

A ball rolls along a horizontal track in a certain time. If the track has a small upward dent in it, the 7) time to roll the length of the track will be

the same

A cart maintains a constant velocity of 100 m/s for 10 seconds. During this interval its acceleration is

zero