Falling Objects – Balanced and unbalanced forces

If the forces on an object are balanced, there is no resultant force.
The object stays still, or carries on at a constant speed.

If an object is standing still, then a (resultant) force is needed to start it moving.

If it is already moving, then a force is needed to make it accelerate or decelerate.

A force is also needed to make it change direction.
The diagram shows a
sky-diver.
He has jumped out of a
helicopter.
1
At the start, there is only one force
on the sky-diver. This is his w______.
This unbalanced (or r____________ )
force makes him gain speed, or
a____________ .
Fill in all the missing words:
As he travels faster, the friction (called
a____ r______________ ) increases.
When the 2 forces are equal, he
stops a_________________ and travels
at a constant s _________ .
This speed is called his terminal
velocity.
2
3
The sky-diver weighs
700 N.
Label each of the
forces in all of the
diagrams with one of
these labels:
 700 N
 less than 700 N
 more than 700 N
Explain carefully what
happens when his
parachute opens, using
the correct scientific
words.
Level of understanding
Emerging
Developing
Secure
When his parachute opens, the
a ____ r _______________ increases.
This makes him slow down, until . . .
. . . the 2 forces are equal.
Because the 2 forces are b__________ ,
the r____________ forces is z______.
So he travels at constant s______.
Mastery statement: Understanding Scientific processes
I can name forces acting on falling objects.
I can describe how the forces on the skydiver change as she/he falls.
I can explain how the change in forces affect the speed of the skydiver at different
stages e.g. at the start, before and after the parachute opens.
Tick
The Skydiver’s Journey – Help sheet
Describe how a skydiver reaches her terminal velocity before she opens her
parachute. Explain how after she opens her parachute, she has a new, lower
terminal velocity.
Emerging
Name the two forces
acting on the skydiver as
he falls from the plane
Secure What happens to
the air resistance as she
opens her parachute?
Developing
Explain how air
resistance changes as
the skydiver get faster.
Secure
What is terminal
velocity?
Secure
Explain why she reaches
her terminal velocity.
Sentence Starters:
The two forces acting on her are...
As she gets faster, the air resistance...
Terminal velocity is a... The skydiver reaches her terminal velocity when...
The parachute causes the...
Velocity
Velocity-time graph for a Skydiver
0
Time
-Terminal velocity reached - Speed increases
- Diver hits ground – Parachute opens, diver slows down
- Lower terminal velocity reached