Download YEAR 7 SCIENCE HOMEWORK /YOU ARE A SCIENTIST 1

YEAR 10 SCIENCE HOMEWORK – 4 / MOTION
GRAVITY AND ACCELERATION
 COMPREHENSION: Read and answer the questions below.
If you step off a tall building you will fall. Gravity exerts a force on your body and
pulls you towards the ground. The further you fall, the faster you fall. This is
because you are being accelerated as you fall. Large people and small people
accelerate at the same rate. Gravity causes acceleration on all objects. They are
accelerated towards the centre of the Earth.
There is a speed limit to falling. As you fall through the air, the air pushes back
against you. This is air resistance, and it is a type of friction. The highest speed you
can reach by falling is called terminal velocity. It depends on the amount of air
resistance you have in your fall. Parachutists in free fall reach 200 km/h (60 m/s).
They slow considerably when they open their parachutes. A parachute provides
much more air resistance.
There is a story that the famous scientist, Galileo Galilei, in the 1500s, dropped a
large iron cannon ball and a small iron ball from the Leaning Tower of Pisa. He
wanted to know if they hit the ground at the same time. People suspected that the
larger cannon ball would hit the ground first because it was heavier. However the
observers saw that both balls hit the ground at the same time.
When the NASA astronauts were on the moon, they did a similar experiment. They
dropped a feather and a hammer, and filmed it with a movie camera. They, like
Galileo, wanted to know if the acceleration was the same for different objects. There
is no atmosphere on the moon to slow falling objects with air resistance like there is
on Earth. The feather and hammer hit the surface of the moon at the same time.
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Why do you fall down when you jump off something?
What is terminal velocity?
What is it about the parachute that shows a parachutist down?
Why did NASA do their test on the moon instead of the earth?
Why were people surprised at the results of Galileo’s experiment?
 Write down True or False for each statement
1. Gravity exerts a force on your body and pulls you towards the centre of the
earth.__________
2. Heavy things are accelerated by gravity much faster than small and light
things.___________
3. A parachute provides much more air resistance than a person, which is why it
slows a person down.___________
4. Terminal velocity is the speed you have to be travelling at to be killed in a
crash.__________
5. If you dropped a hammer and a feather together on the earth they would hit
the ground at exactly the same time.___________
Paste this homework sheet in your science book.