# U1.1 grade 4 forces and motion

```Unit 1: Forces and
Energy
Lesson 1: Forces
and Motion
Lesson 1: Forces and Motion
Acceleration
Force
Describe motion
and its factors.
Explain speed,
velocity and
acceleration.
Relate the
forces to the
above terms.
Compare
balanced and
unbalanced
forces
Friction
Inertia
Motion
Speed
Velocity
State the
definitions of
gravity and
friction forces
Lesson 1: Forces and Motion
• What did you notice about the sky diver?
• How does their position affect their fall?
• Would splaying their arms and legs affect their
speed?
• How would their fall change if their parachutes
open?
Lesson 1: Forces and Motion
• What if the sky diver opened the
parachute?
Lesson 1: Forces and Motion
• By changing the shape and position of
their bodies, the skydivers can change the
speed at which they fall.
• They fall slowest in belly-to-Earth position
because the drag force is greatest.
• They fall fastest when they streamline
their bodies and minimize drag.
Lesson 1: Forces and Motion
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The position of an object is its location.
Motion is a change in an object’s position.
Motion of an object is related to:
Its distance covered
Its direction
Its time passed
Lesson 1: Forces and Motion
• The speed of an object is how fast an
object position changes over time.
• Unit of speed is distance per time
• (m/s) meter per second
• (km/h) kilometers per hour
Lesson 1: Forces and Motion
• Velocity is the speed and
the direction of an
object.
• Velocity have the same
unit of speed but it should
include the direction.
• Ex : plane is flying 640
km/h  This is the speed.
• Ex: plane is flying 640
km/h south  This is the
velocity.
Lesson 1: Forces and Motion
• Acceleration a change in velocity over
time.
• When an object speeds up, slows down, or
change its direction  it accelerates.
• And only sometimes if its direction
changes it accelerate.
Lesson 1: Forces and Motion
Increase
Decrease
Change its direction
Lesson 1: Forces and Motion
• A force is any push or pull.
• The acceleration of an object depends on how
much force is there.
• More force more acceleration
• Less force less acceleration
• Also acceleration depends on weight of an object.
• More weight less acceleration
Lesson 1: Forces and Motion
Lesson 1: Forces and Motion
• P: 12 # 1:
• What two factors affect acceleration?
• Force and Weight
• P: 12 # 2:
• How would you increase the speed of a toy
car?
• Increase the force of push or decrease the
weight of the car.
Lesson 1: Forces and Motion
• Forces that add up on same directions
produce stronger force.
• Forces that add up in opposite directions
produce weaker force.
• Total forces on an object is the sum of all
forces acting on the object.
Lesson 1: Forces and Motion
• Forces acting on object
without changing its motion
is called balanced forces.
• Objects at rest
• Objects in motion but not
accelerating
• Sum of forces on this object
should be equal to zero.
Lesson 1: Forces and Motion
• Forces that do not add up to zero are
unbalanced forces.
• Change in motion
• Change in speed
• Change in direction
Lesson 1: Forces and Motion
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Sum is zero
Sum is not zero
No acceleration
Change in direction, motion and speed.
Balanced
forces
Unbalanced
forces
Lesson 1: Forces and Motion
• Inertia is the tendency of an object in
motion to stay in motion or of an object at
rest to stay at rest.
Lesson 1: Forces and Motion
• Gravity and friction are two forces that can
act on an object.
• Gravity is a non contact force that pulls
the objects toward each other.
• Friction is a contact force that slows or
stops the objects from moving.
```