Push Pull

force A force is any push or pull that causes a - - - - - - resting object to move

force A force is any push or pull that causes a - - - - - - resting object to move - - - moving object to accelerate

Fundamental Forces Gravity

Fundamental Forces Electromagnetism

Fundamental Forces Strong Nuclear

Fundamental Forces Weak Nuclear

Contact Forces

Contact forces These are forces that require some contact You push a cart – it moves You catch a ball – it stops moving

At-a-distance Forces

At-a-distance forces These are forces that act without contact The attraction of gravity The repulsion of two poles of a magnet

Balanced Forces

Balanced force A force in which the net force is equal to zero All the forces acting on an object must be taken into account

Balanced forces

UnBalanced force A force in which the net force is greater than zero All the forces acting on an object must be taken into account

Unbalanced forces

Problem Jimmy drops 5.0 kg box of shingles (50 N force) off the roof of his house into the swimming pool below. The box hits the water and encounters a 50 N force of resistance upward.

Which velocity-time graphs best describes the motion of the box?

Frictional Force

Friction force A force that always opposes motion Static friction – the friction that is present between two stationary objects Kinetic Friction – the friction that develops between two moving surfaces

Friction force Static

Friction force Kinetic

Problem set balanced forces unbalanced forces

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3 If the net force acting upon an object is 0 N, the object MUST _____________. a. be moving erratically b . be accelerating c. be at rest d. be moving with a constant speed in the same direction e. either c or d

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Force symbolics

Applied Force The force applied to an object by a person or another object Our symbol: F

Gravity The force that is directed "downward" towards the center of the Earth Our symbol: W

Normal The “support” force exerted upon an object that is in contact with another stable object. Our symbol: N

Frictional The force exerted by a surface that opposes the movement of an object across it. Our symbol (static): fS Our symbol (kinetic): fK

Air resistance A special type of frictional force that acts upon objects as they travel through the air Our symbol: Fair

Tension The force transmitted through a string, rope, cable or wire when pulled tight by forces acting from opposite ends Our symbol: T

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