speed up 加速 查看更多

 

題目列表(包括答案和解析)

 

Falling and gravity

About 400 years ago, Caltleo

noticed that objects speed up,

or accelerate, as they fall.

 

He found that heavy and light

things, of the same shape and

size, take the same time to fall

to the ground. Gravity pulls

then-* down equally.

 

Try this for yourself with

different objects, like a slipper :

and a heavy boot.

 

Air resistance

Objects of different shapes and

sizes fall at different rates.  The

shape of a parachute makes

people fall more slowly.

 

 

The air pushing

against the parachute

causes a lot of air

resistance*. A person

without a parachute

falls faster because less

air pushes against

them.

The faster something falls, the

more air resistance there is on

it. Eventually, the air resistance

 slowing it down becomes as

strong as the pull of gravity.

Then its speed no longer

changes. This is called terminal

speed.

Free fall

If there were no air, there would be no air

resistance. All falling objects would just get

faster and faster < called is This rate. same the>

free fall.

 

67. Falling objects are pulled down to the ground by   .  

A. gravity                         B. resistance              C. speed                   D. acceleration(加速度)  

68. Why do people make parachutes(降落傘)?  

A. To look pretty and colourful in the air.            B. To slow down the falling speed.  

C. To push against the air in the sky.                  D. To accelerate the falling movement.  

69. Which did Galileo discover?  

A. A heavy ball falls faster than a light ball.          B. A light ball falls faster than a heavy ball.  

C. A light ball and a heavy ball fall at the same speed

D. A light ball and a heavy ball fall at different speed.

70. Which of the following is NOT true according to the passage?

A. Heavy and light objects fall equally when they are different in size.

B. When air resistance equals gravity, objects fall at terminal speed.

C. Without air; all falling objects get faster and faster at the same rate.

D. Slippers(拖鞋) and boots (靴子)fall at the same speed because they have the same shape  

 

查看答案和解析>>

 

Falling and gravity

About 400 years ago, Caltleo

noticed that objects speed up,

or accelerate, as they fall.

 

He found that heavy and light

things, of the same shape and

size, take the same time to fall

to the ground. Gravity pulls

then-* down equally.

 

Try this for yourself with

different objects, like a slipper :

and a heavy boot.

 

Air resistance

Objects of different shapes and

sizes fall at different rates.  The

shape of a parachute makes

people fall more slowly.

 

 

The air pushing

against the parachute

causes a lot of air

resistance*. A person

without a parachute

falls faster because less

air pushes against

them.

The faster something falls, the

more air resistance there is on

it. Eventually, the air resistance

 slowing it down becomes as

strong as the pull of gravity.

Then its speed no longer

changes. This is called terminal

speed.

Free fall

If there were no air, there would be no air

resistance. All falling objects would just get

faster and faster < called is This rate. same the>

free fall.

67. Falling objects are pulled down to the ground by  

A. gravity                         B. resistance              C. speed                   D. acceleration(加速度) 

68. Why do people make parachutes(降落傘)? 

A. To look pretty and colourful in the air.            B. To slow down the falling speed. 

C. To push against the air in the sky.                  D. To accelerate the falling movement. 

69. Which did Galileo discover? 

A. A heavy ball falls faster than a light ball.          B. A light ball falls faster than a heavy ball. 

C. A light ball and a heavy ball fall at the same speed

D. A light ball and a heavy ball fall at different speed.

70. Which of the following is NOT true according to the passage?

A. Heavy and light objects fall equally when they are different in size.

B. When air resistance equals gravity, objects fall at terminal speed.

C. Without air; all falling objects get faster and faster at the same rate.

D. Slippers(拖鞋) and boots (靴子)fall at the same speed because they have the same shape 

查看答案和解析>>


D
The price of gas has been going up. We do not know when it will end. Many people want to know how they can save gas. The best way to save gas is to change driving habits.
The accelerator (加速器) or gas pedal, has a lot to do with how much gas you use. The faster you drive, the more gas you use. Drivers should slow down a bit to save gas. Driving at a steady speed helps to save much gas you use. Accelerating slowly to get to the speed you want to go helps save gas too.
The more you drive your car, the more gas you use. Think about the places you need to go before leaving your home. You should run as many errands (差事) that you need to do in one trip. Always try to pick the shortest route when going somewhere.
Cars that are in good working condition use less gas. Take care of your car. Make sure the engine is running well and is tuned up often. Have a repairman check it if something seems wrong.
Tires are important too. Keep the tires inflated (飽滿) properly on a car. It will help the car roll better and will get you better mileage (英里數(shù)) If the tires of a car are worn then they should be replaced.
Finally, think about using your car less. Walk or ride a bike if you do not have far to go. Carpool (合伙用車) or take public transportation when you can. Leaving your car at home really saves gas.
There are many ways a person can save gas. These are just a few ideas that can help you save some money at the gas pump. Try changing the way you drive and see how much it saves you!
68. Which of the following can help save gas?
A. Driving as fast as you can.
B. Accelerating quickly to get to the speed you want.
C. Driving fast a little now and slowly a little then.
D. Driving at a speed that is, seldom changed.
69. The underlined sentence in the 3rd paragraph probably means you should
A. do as many things as you can in one trip
B. go to as many places as you can in one trip
C. take as many people as you can in one trip
D. use as many ways of driving as you can in one trip.
70. Which of the following is NOT true according to the passage?
A. Always keep your car in good working condition.  B. Never use your car unless it is necessary.
C. Replace your tires if they are worn out.                 D. Always stick to your own driving habits.
71. Which would be the best title for the passage?
A. How to use your car correctly.
B. How to save gas when using your car.
C. How to deal with the price of gas.
D. How to form good driving habits.

查看答案和解析>>

D

The price of gas has been going up. We do not know when it will end. Many people want to know how they can save gas. The best way to save gas is to change driving habits.

The accelerator (加速器) or gas pedal, has a lot to do with how much gas you use. The faster you drive, the more gas you use. Drivers should slow down a bit to save gas. Driving at a steady speed helps to save much gas you use. Accelerating slowly to get to the speed you want to go helps save gas too.

The more you drive your car, the more gas you use. Think about the places you need to go before leaving your home. You should run as many errands (差事) that you need to do in one trip. Always try to pick the shortest route when going somewhere.

Cars that are in good working condition use less gas. Take care of your car. Make sure the engine is running well and is tuned up often. Have a repairman check it if something seems wrong.

Tires are important too. Keep the tires inflated (飽滿) properly on a car. It will help the car roll better and will get you better mileage (英里數(shù)) If the tires of a car are worn then they should be replaced.

Finally, think about using your car less. Walk or ride a bike if you do not have far to go. Carpool (合伙用車) or take public transportation when you can. Leaving your car at home really saves gas.

There are many ways a person can save gas. These are just a few ideas that can help you save some money at the gas pump. Try changing the way you drive and see how much it saves you!

68. Which of the following can help save gas?

A. Driving as fast as you can.

B. Accelerating quickly to get to the speed you want.

C. Driving fast a little now and slowly a little then.

D. Driving at a speed that is, seldom changed.

69. The underlined sentence in the 3rd paragraph probably means you should

A. do as many things as you can in one trip

B. go to as many places as you can in one trip

C. take as many people as you can in one trip

D. use as many ways of driving as you can in one trip.

70. Which of the following is NOT true according to the passage?

A. Always keep your car in good working condition.  B. Never use your car unless it is necessary.

C. Replace your tires if they are worn out.                 D. Always stick to your own driving habits.

71. Which would be the best title for the passage?

A. How to use your car correctly.

B. How to save gas when using your car.

C. How to deal with the price of gas.

D. How to form good driving habits.

 

查看答案和解析>>

D

The price of gas has been going up. We do not know when it will end. Many people want to know how they can save gas. The best way to save gas is to change driving habits.

The accelerator (加速器) or gas pedal, has a lot to do with how much gas you use. The faster you drive, the more gas you use. Drivers should slow down a bit to save gas. Driving at a steady speed helps to save much gas you use. Accelerating slowly to get to the speed you want to go helps save gas too.

The more you drive your car, the more gas you use. Think about the places you need to go before leaving your home. You should run as many errands (差事) that you need to do in one trip. Always try to pick the shortest route when going somewhere.

Cars that are in good working condition use less gas. Take care of your car. Make sure the engine is running well and is tuned up often. Have a repairman check it if something seems wrong.

Tires are important too. Keep the tires inflated (飽滿) properly on a car. It will help the car roll better and will get you better mileage (英里數(shù)) If the tires of a car are worn then they should be replaced.

Finally, think about using your car less. Walk or ride a bike if you do not have far to go. Carpool (合伙用車) or take public transportation when you can. Leaving your car at home really saves gas.

There are many ways a person can save gas. These are just a few ideas that can help you save some money at the gas pump. Try changing the way you drive and see how much it saves you!

68. Which of the following can help save gas?

A. Driving as fast as you can.

B. Accelerating quickly to get to the speed you want.

C. Driving fast a little now and slowly a little then.

D. Driving at a speed that is, seldom changed.

69. The underlined sentence in the 3rd paragraph probably means you should

A. do as many things as you can in one trip

B. go to as many places as you can in one trip

C. take as many people as you can in one trip

D. use as many ways of driving as you can in one trip.

70. Which of the following is NOT true according to the passage?

A. Always keep your car in good working condition.  B. Never use your car unless it is necessary.

C. Replace your tires if they are worn out.                 D. Always stick to your own driving habits.

71. Which would be the best title for the passage?

A. How to use your car correctly.

B. How to save gas when using your car.

C. How to deal with the price of gas.

D. How to form good driving habits.

查看答案和解析>>


同步練習(xí)冊答案