Forces & Newton's Laws

Forces & Newton's Laws

Forces Quiz:

This quizziz reviews the concepts, newton's 1st two laws, simple math. ​

​Q

BLUE SHEETS OUT. SCRATCH PAPER OUT.

PUT AWAY EVERYTHING ELSE

• Use Blue sheets as needed.

• Add notes to blue sheet as needed

• Ask questions.

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Force	A pushing or pulling interaction that can cause objects to accelerate. unit: Newtons (N)
Acceleration	How quickly an object speeds up/slows down or changes direction (how abrubtly the motion changes) unit: m/s/s
NET, UNBALANCED FORCE CAUSES ACCELERATION NO FORCE IS NEEDED TO CAUSE OR MAINTAIN VELOCITY!

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NEWTON’S FIRST LAW (what forces do)	(1) Objects do NOT change their motion(speed up, slow down or turn) UNLESS forced to by a net, outside force. (2) UNBALANCED Forces cause Acceleration; BALANCED Forces result in constant velocity motion.
NEWTON’S 2nd LAW (how much acceleration)	Conceptual version : The acceleration of an object is directly related to the Net Force ON the object and inversely related to the mass of the object.

Multiple Choice

FORCES ARE

• actions

• reactions

• interactions

Multiple Choice

The Unit of Force is

• N

• F

• kg

• m/s/s

Multiple Choice

Objects with balanced forces ALWAYS have

• 0 velocity

• 0 mass

• 0 acceleration

• 0 gravity

Multiple Choice

Unbalanced forces are needed to

• keep an object moving in a straight line

• keep an object moving at constant speed

• change an object's velocity

Multiple Choice

A comet is moving through space, far from any stars or sources of gravity. The speed of the comet will

• decrease quickly with no gravity around

• gradually decrease

• remain constant

• increase until the comet hits something

Multiple Choice

A car and driver are driving in a straight line at 45 miles per hour. The net force on the car is

• Unbalanced - the engine is running

• Unbalanced - there is always friction on the car

• balanced - the car is not accelerating

Multiple Choice

A car and driver are driving in a straight line at 45 miles per hour when the driver slams on the breaks. The car quickly slows down. The driver feels thrown forward until the seatbelt catches him.

The car quickly slows because the net forces are ...

• Unbalanced - the break force is causing an acceleration

• Balanced - the car does not speed up

• balanced - the car is not accelerating

Multiple Choice

A car and driver are driving in a straight line at 45 miles per hour when the driver slams on the breaks. The car quickly slows down. The driver feels thrown forward until the seatbelt catches him.

The person feels thrown forward because the forces are

• Unbalanced - the force of the seat pushes him forward

• Unbalanced - the brakes push him forward

• balanced - the man is not accelerating, he just continues moving the way he was

Multiple Choice

An astronaut is floating motionless in outer space - far from any gravity or friction. The astronaut has a small jet pack that has enough fuel for a 4 second blast. (which provides a net force) If the astronaut uses the 4 second blast - how will motion be affected?

• Astronaut will move forward for 4 seconds, then slow down and stop.

• Astronaut will speed up for 4 seconds, then keep moving at constant speed.

• Astronaut will move forward for 4 seconds, then drift back to starting point.

• astronaut will speed up for 4 seconds and then slow down

Multiple Choice

What happens to an object when the NET FORCE on it is zero?

• it will have 0 acceleration

• it will have constant velocity

• all forces are balanced

• all of the above

Multiple Choice

With NO NET FORCE - Objects in motion will ......

• Slow down and stop

• move with constant velocity

• speed up forever

Multiple Choice

With NO NET FORCE - Objects in motion will move with constant velocity. Is one way of stating which law?

• Newton's 1st Law

• Newton's 2nd Law

• Newton's 3rd law

Multiple Choice

A man pushes a car with 500N of force, while the ground exerts 100N of friction.

The same man later pushes a lawnmower with 500 N of Force. and the ground again exerts 100N of Friction.

Which Object will have the greatest NET FORCE

• The Car

• The Lawnmower

• Both are the same

Multiple Choice

A man pushes a car with 500N of force, while the ground exerts 100N of friction.

The same man later pushes a lawnmower with 500 N of Force. and the ground again exerts 100N of Friction.

Which Object will have the greatest ACCELERATION

• The Car, because it has a bigger mass and the same net force

• The Lawnmower, because it has a smaller mass and the same net force

• Both are the same, since the Net Force is the same

Multiple Choice

A 1000 kg car is accelerating to the left at 5 m/s/s. What is the net Force on the car?

• 5 m/s/s left

• 1000 kg

• 5000 N left

• Cannot tell without knowing the applied forces and friction force.

Multiple Choice

A 10,000 kg rocket is accelerating upward at 2 m/s/s. What is the Net Force on the rocket?

• 2 N up

• 10,000 N up

• 20,000 N up

• Not enough information

Multiple Choice

The force that is exerted by a rope or string is called

• Normal Force

• Tension Force

• Applied Force

• Pull Force

Multiple Choice

The force that the ground exerts on you is called

• Normal Force

• Tension Force

• Applied Force

• Pull Force

Multiple Choice

A car drives around a race track at a constant 50 m/s. Is there a Net Force acting on the car?

• NO - because the speed is constant

• YES - because all moving objects have a NET Force

• YES - because the velocity is NOT constant

Multiple Choice

The car shown has 4 different forces acting on it.

What is the NET FORCE in the up/down direction

• 0 N

• 2400 N Up

• 3600 N down

• 16,000 N up

• 19,600 N down

Multiple Choice

The car shown has 4 different forces acting on it.

What is the NET FORCE in the left/right direction

• 0 N

• 2400 N right

• 3600 N right

• 16,000 N left

• 19,600 N left

Multiple Choice

The car shown has 4 different forces acting on it.

The Net Horizontal Force is 2400 N right.

What is the ACCELERATION in the left/right direction

• 0 m/s/s

• 1 m/s/s Right

• 2 m/s/s Left

• 3 m/s/s Right

Multiple Choice

A tablecloth, plate, cup, and candle are sitting on a table not moving.

A man pulls a table cloth very quickly.

The tablecloth comes off of the table, while the objects on the table (plate, cup, candle) do not move.

Why does the table cloth move?

• The man provides a net force, so the cloth accelerates

• The man makes sure the forces on the cloth are balanced - so it moves

• The cup, plate and candle are not too heavy.

Multiple Choice

A tablecloth, plate, cup, and candle are sitting on a table not moving.

A man pulls a table cloth very quickly.

The tablecloth comes off of the table, while the objects on the table (plate, cup, candle) do not move.

Why do the objects stay on the table?

• Newton's 2nd Law: not enough mass to accelerate

• Newton's 1st Law: objects stay at rest unless forced (and no force added on the objects)

Poll

My Understanding of Forces is

• Very Strong

• Pretty Strong

• OK - but need some review

• Not Good - need to relearn most of this

• Very Low - I will be coming to office hours next week and working on my class focus.