Welcome Scientists!

Today:Return and Go Over Formative QuizReview For Force and Motion Test

Match each of the following:

A. The car is stopped

B. The car is traveling at a constant speed

C. The speed of the car is decreasing

• Graph 1 matches description B because the distance is increasing by the same amount over time.

• Graph 2 matches description A because the distance is staying the same as time goes on – this means that its distance isn’t increasing or decreasing – it is sitting still.

• Graph 3 matches description C because at first, the distance is increasing with a steep slope and then levels off. This means that the distance isn’t increasing as fast so it isn’t going as fast.

1. A sailboat travels 100 meters in 50 seconds.v = d/t

v = 100 m/50 s

v = 2 m/s

2. A dog running through a field if he is covering 23.7 meters in 54 seconds.

v = d/t

v = 23.7 m/54 s

v = 0.44 m/s

3. A bicycle rider travels 50.0 Km in 2.5 hours.v = d/t

v = 50.0km/2.5 h

v = 20 km/h

•Answer the following questions and then explain which of Newton’s Laws is being described.

7. Heavier football players tend to play on the offensive or defensive line. Why? Because

you need more force to change their motion because they have more mass.

8. This demonstrates Newton’s Second Law because the force needed to accelerate

them is proportional to their mass - more mass requires more force.

9. Imagine you are pulling a wagon with a ball in it. You suddenly stop the wagon.

Describe what will happen to the ball at first the ball will be at the back of the wagon.

When you stop the wagon, the ball will roll forward until it hits the front of the

wagon. The ball might bounce out of the front of the wagon if it is going fast enough.

10. This demonstrates Newton’s First Law because the ball is moving and when you stop

the wagon it will keep moving because you are putting a force on the wagon, not the

ball. Since you are not putting a force on the ball it will continue in motion because

things in motion tend to stay in motion unless acted on by an unbalanced force.

11. Which of Newton's laws relate acceleration to mass?

12.Which of Newton's laws is also called the law of inertia?

13.Which of Newton's laws allows a rocket to accelerate into the air

by burning rocket fuel?

14.Which of Newton's laws explains what happens when two

skaters push apart on an ice rink?

15.Which of Newton's laws governs what happens when a

tablecloth is pulled out from under a table full of dishes without

damaging them?

16.Which of Newton's laws is also called the law of action/reaction?

2nd

1st

3rd

3rd

1st

3rd

• Box 1 will fall and accelerate because the force of 5N down is unbalanced but the forces of 5N to the right and left balance each other out.

• Box 2 will stay stationary because each force is balanced by an equal force in the opposite direction.

• Box 3 will fall and accelerate but not as fast as box 1 because while the forces to the left and right are balanced there is a net force of 3 N pulling down. Box 3 won’t accelerate as much as Box 1 because it is being pulled down with less force.

• Box 4 will accelerate up and to the right because there are unbalanced forces in those directions

• List and describe at least 3 forces shown in the diagram and describe the direction in which the force is acting. Explain clearly.

• For example: The diagram shows the force of… because…this force is pulling/pushing (direction)

1. The diagram shows an applied force because the girl is pushing on the pedals of the bike to cause her to move forward.

2. The diagram shows the force of gravity because we can assume she is on earth and gravity is always acting on objects on earth.

3. The diagram shows the normal force because she is on a surface and is not falling through the planet. This force is pushing up against gravity.

4. The diagram shows drag and friction pushing against the motion of the bike because the wheels are in contact with the road and the bike is colliding with air molecules which slows it down.

Draw a free-body diagram for the girl on the bike.

FN

Fg

FAFdrag

Ff

Definitions• Force- a push or a pull• Balanced forces – forces that are equal and

opposite or when an object has a net force of zero (all the forces cancel each other out)

• Unbalanced forces – at least one of the forces on an object is not canceled out

• Net force – any “leftover” unbalanced force on an object – the sum of all forces on an object Motion – the change in position of an object

• Free-body diagram – shows all the forces acting on an object but doesn’t show the environment – only shows the object as a dot or a square

• Normal force – exists when an object is on a surface and keeps objects from falling to the center of the earth. Fn is always perpendicular to the surface the object is on

• Gravitational force- force of attraction between any two or more masses

• Applied force – a push or a pull on an object by another object or living thing

• Friction – a force that opposes motion when the surfaces of objects are in contact with each other

• Air resistance – a type of friction caused by moving objects colliding with air molecules

• Acceleration – the change in an objects velocity over time – how much an object speeds up or slows down during a period of time

• Average speed – how much an object’s distance or location changes in a period of time ave. v = d/t

• Instantaneous speed - actual speed of an object at any particular moment

• Inertia – the tendency of an object to resist changes in its motion (more mass means more inertia)

• Newton – unit of measure of force• Action/Reaction – (3rd Law) • F=ma – (2nd Law) force is proportional to mass and

acceleration• Mass - amount of matter in an object