2.2 Resultant force

1. 6 + 5 =2. 15 – 10 = 3. 3a + 5a = 4. 100N – 50N =5. 40 – 40 =6. 100N – 200N =7. 50kN – 25kN = 8. 1kN – 500N =

April 22, 2023

Try these sums

2.2 Resultant force

1. 6 + 5 = 11 2. 15 – 10 = 53. 3a + 5a = 8a4. 100N – 50N = 50N5. 40 – 40 = 06. 100N – 200N = -100N7. 50kN – 25kN = 25kN8. 1kN – 500N = 500N (1k =

1000)

April 22, 2023

2.2 Resultant force

• What is a resultant force?• What happens if the resultant force is zero?• What happens if there is a resultant force?

April 22, 2023

Voyager 2 was launched in 1974. Since then it has had no main rocket engine to power it. The spacecraft is now at the edge of the Solar System travelling at 60 000 mph!

How can it keep going?

Resultant force

• A single force used to represent all the forces on an object.

10N 20N 10N

Resultant

=

=

20N

10N

?

What is the missing resultant force?

Newton’s 1st Law of motion

When the resultant force on an object is zero:•An object stays still•Has a constant velocity

Explain how a skater carries on moving with no effort on ice. Which force is zero on ice?

When the resultant force is not zero the object changes its velocity.

What happens when the:

1. Weight is more than the Lift force?

2. Lift is more than the Weight?

3. Weight equals the Lift?

Accidents

Draw a diagram to show the lorry hitting the car. Include:

1. The direction the lorry was travelling

2. The force needed to stop the lorry

3. The force on the car.

Investigation

Use a trolley to look at Newton’s 1st Law.• How can you get the trolley to move

at a constant speed?• Which forces must be balanced for this

to happen?

When the resultant force on an object is zero:•An object stays still•Has a constant velocity

books Trolley

Key Points

Start Resultant Force Effect on object

1 At rest Zero Stays at rest

2 Moving Zero Velocity stays the same

3 Moving In direction of movement.

Accelerates

4 Moving Against direction of movement

Decelerates

Copy this table