Lesson 1, Energy - Grade 7

Who does work from the following mixes

• A person pushes a wall.

• A person plays football.

• A person sleeps.

•  A person studies, while he is sitting.

A force of 10 newton affects a body to move it a distance 5 m., so the work done is ----- joule.

• 5

• 30

• 50

• 150

If the force decreases by half and the displacement is doubled, so the work.........................

• is doubled.

• decreases to half.

• doesn't change.

• increases to four

  times

 If a man acts on a car by a force equals 50 N. and the car doesn't move a distance, so the work done by the man equals...……......

• zero

•  50 J

•  100 J

• 1000 J

Food and fuel are sources of…………… energy.

• chemical

•  mechanical

• electric

• sound

Resource of permanent energy is................

• petrol.

•  the Sun.

• nuclear reaction.

•  coal.

 …………….. is an example of the sources of electric energy.

• Electric fan

• Oil lamp

• Oven

• Solar cell

 …………………. is from the clean sources of energy which doesn't pollute the environment.

• Petrol

• Coal

• Wood

• Wind

Chemical energy can be stored in…………………….

• car battery

• raising a load upwards

• stretched spring

• car lamps

Weight of the body on the Earth equals its……………………..

• mass + gravity acceleration.

• mass x gravity acceleration.

• mass + gravity acceleration.

• mass — gravity acceleration.