DO NOW: BELL RINGER

BALANCED VS UNBALANCED FORCES

AGENDA• Bell Ringer

• PowerPoint with Cornell Notes

• Net Force

• Balanced Force

• Unbalanced Force

• Distance-Time Graphs

• 10 Minute Net Force Challenge

• Worksheet

• Exit Slip

FORCE RECAP

• A force is a push or pull.

• Force is measured in Newtons (N).

• There are contact and non-contact forces.

• Contact forces such as applied force, normal

force, friction and air resistance work through

direct contact.

• Non-contact forces such as gravity, magnetism,

and electrical force work at a distance.

• The universal law of gravitation states that all

objects have this force of attraction. Mass and

distance affect the force of gravity.

NET FORCE

• Add when the forces are working together.

• Subtract the bigger number minus the smaller

number when the forces are working against each

other.

The sum of the forces acting on an

object.

NET FORCE PRACTICEGroup Activity

5N

10N

8N 8N

4N

20N

Answer:

Answer:

Answer:

N

BALANCED FORCES: HAVE A

NET FORCE OF 0 N• If the forces acting on a still object are

balanced, the object doesn’t move.

• If the forces acting on a moving object

are balanced, the moving object will

not change speed or direction.

• Balanced forces have a net force of

zero.

Drag is a mechanical force. It is generated by the interaction and

contact of a solid body with a fluid (liquid or gas).

Drag is a Resistance

to motion through a

fluid

UNBALANCED FORCES: HAVE A NET FORCE GREATER THAN 0.

• One of the opposing forces is greater.

• The object accelerates. That means it

moves, or speeds up, in the direction of

the greater force.

THINK!• The heavier something is, the harder it will be to

move it. The less massive something is, the less force

you will need to move it.

I’d like to

see you

try…Pick on someone

your own size!

NET FORCE?

BALANCED OR UNBALANCED?

Can you name this force?

50 N40 N

Net Force = 10 N to the left

Drag is a mechanical force. It is generated by the interaction and

contact of a solid body with a fluid (liquid or gas).

CALCULATING NET FORCE5- 10 MINUTE CHALLENGE

PRACTICE QUESTIONS

A spacecraft orbiting Earth moves to an orbit that is half as

far from the center of Earth. How does the gravitational

force between the spacecraft and Earth change?

A The gravitational force decreases.

B The gravitational force remains unchanged.

C The gravitational force increases.

D The gravitational force has effect only at Earth’s surface.

Students will describe the relationship among distance,

mass, and gravitational force between any two objects.

What characteristics can you use to describe a

force?

A. The direction in which it acts and its strength

B. Only the direction in which it acts

C. Only its strength

D. Its speed and the direction in which it acts

Aito carried out an experiment to separate the components in a mixture. The steps Aito took are shown in the illustration below .

What forces did Aito depend

upon to separate the

components in this mixture?

A magnetic and electrical forces

B gravitational and electrical forces

C magnetic and gravitational forces

D balanced and unbalanced forces

Which of the following is true about mass and

weight?

F. Mass and weight are not related.

G. Mass is always the same, weight may

change.

H. Weight is always the same, mass

maychange.

I. Mass depends on gravity, weight does

not.

At baseball practice, Takahiro and Alfredo both picked up the same bat and neither would let go until one of them had it for himself. Takahiro pulled the bat with a force of 15 newtons (N), while Alfredo pulled with a force of 20 newtons(N). Why did Alfredo end up with the bat?

a. because the net force was 5 N in Alfredo’s direction.

b. because the net force was 20 N in Alfredo’s direction.

c. because the force was 5 N in Takahiro’s direction.

d. because the net force was 15 N in Takahiro’s direction.

Leanna decided to rearrange her

bedroom by moving her dresser to the

opposite wall. She tried pushing it, but

found that the dresser would not move.

What force was Leanne NOT able to

overcome?

A. electrical force

B. magnetic force

C. balanced force

D. frictional force

Multiple forces can act on the same

object at the same time. When will two

forces acting on the same object result in

an unbalanced force on that object?

A. when the two forces cancel each other

b. when the two forces produce a net

force of 0 N

c. when the two forces apply different

forces from opposite directions

d. when the two forces apply the same

amount of force from opposite directions

Becky asked her classmate Manuel to help

her move a table to the other side of the

classroom. Becky pushed the table with a

force of 20 newtons (N) and Manuel pulled

the table, from the opposite side, with a

force of 25 N. What was the net force

acting on the table?

A. 5 N

B. 20 N

C. 25 N

D. 45 N

What characteristics can you use to describe a force?

A. The direction in which it acts and its strength

B. Only the direction in which it acts

C. Only its strength

D. Its speed and the direction in which it acts

The diagrams below show smooth

blocks of wood being pushed across the

same surface. The mass of the block

and amount of force applied are

labeled in each diagram. In which

diagram would the block of wood have

the greatest acceleration?

Each figure below shows a force

measured in Newtons pushing on a

block. If there are no other forces

pushing on the block, in which case is

the acceleration of the block greatest?

EXIT SLIP