Acceleration Coefficient of Friction Equilibrium Force Free Body Diagram Inertia Kinetic Friction Mass

Motion Net Force Newton Rolling Friction Static Friction Terminal Velocity

Vector

Contact – direct contact or touch between objects

Long Range – acts at a distance

Pushing a crate across the floor – Applied Air Friction - Drag Opposes motion – Friction Support force – Normal Created in a rope, etc when connected to

another mass – Tension Force due to gravity – Weight

Are the forces above contact or long range?

Pictorial diagram of all the forces acting on an object

The length of the arrow is proportional to the magnitude of the force

How is the normal force drawn?

How is weight drawn?

Draw a FBD for the following:1.A flowerpot falls freely from a windowsill.2.A skydiver falls at a constant velocity.3.A cable pulls a box across a table. The box

accelerates even though friction is present.4.A rope lifts a bucket.

The vector sum of all forces acting on an object

Calculated for both the x and the y Represented by ΣF

Pictorial diagram of all the forces acting on an object

The length of the arrow is proportional to the magnitude of the force

Law of Inertia An object at rest will stay at rest, an object

in motion will stay in motion unless acted upon by an unbalanced force greater than zero

Ex. A car rider continues forward when the driver suddenly applies the brakes

∑F = ma W = mg Ff = µFn

What is the net force? What is the unit for mass? Is mass the same quantity as weight? What is g? What is μ? On a flat surface, what is equal to the Fn ?

If all of the forces acting on an object balance so that the net force is zero, then

A. The object must be at restB. The object must be at a constant velocity C. The object may be at rest or at a constant velocity

Two astronauts tug on opposite sides of a satellite. The first astronaut tugs to the left with a force of 30 N. With what force does the second astronaut tug in order to keep the satellite moving toward him at a constant velocity of 20 m/s?A. 30 NB. – 30 NC. 0 ND. 50 NE. 1.5 N

The maximum (or terminal) velocity of a skydiver (m=70kg) with arms and legs extended is about 120 mi/h (= 53.6 m/s). What force does air resistance exert on the skydiver?A. 0 NB. 13 NC. 70 ND. 700 NE. 1000 N

An airplane has a mass of 3.1 x 104 kg and takes off under the influence of a constant net force of 3.7 x 104 N. What is the acceleration that acts on the plane?

Weight and mass areA. always the sameB. inversely proportionalC. based on locationD. none of the above

A large (150 kg) refrigerator needs to be moved across the kitchen. Fred pulls with a force of 100 N and Wilma pulls with 75 N in the same direction. If the force of friction was 40 N, what will be the acceleration of the refrigerator?

A 1.17 m/s2

B 0.90 m/s2

C 0.43 m/s2

D 135 m/s2

When a parachutist jumps from an airplane, he eventually reaches a constant speed, called the terminal velocity. This means that

a. the acceleration is equal to g. b. the force of air resistance is equal to zero. c. the effect of gravity has died down. d. the effect of gravity increases as he becomes

closer to the ground. e. the force of air resistance is equal to the

weight of the parachutist.

The force of kinetic friction is always __________ than the force of static friction.

a. less than b. equal to c. greater than d. varies depending on situation

The normal force acts ______________ to the surface of the contact object

a. perpendicular b. parallel c. at an angle

For every action, there is an equal and opposite reaction

A mass is suspended on a spring. The reaction force to the force of the gravity from the Earth acting on the mass is the force exerted by the A. mass on the EarthB. mass on the springC. spring on the massD. spring on the EarthE. Earth on the mass