Physics: “'Cause midterm flunk we not goin to do ….Don't believe me just

watch!” Mid-term review

Constant velocity

Describe:

Steps to make a motion map:

Equations:

displacement=

Velocity=

Units:

When to use:

PRACTICE Problems:

Billy Bob is standing +500 meters away from Sally Shoppingcart and sees Sally rip up her Physics

homework. Billy Bob then runs to Sally with a velocity of – 9 m/sec.

When does Billy Bob get to a point 50 meters from Sally?

What is Billy Bob’s displacement?

Motion map:

Fill in blanks using the graph to the right

xi = _______ xf = _______ d

= _______ t = _______

v = _______

Kinematics

Describe:

The difference between a constant velocity motion map and a changing velocity motion

map:

Equations:

acceleration=

units:

displacement ∆x =

or ∆x =

or ∆x =

When to use:

PRACTICE Problems:

Roy is sitting in his free-rolling office chair and is holding a fire extinguisher. At first, he pushes off the

wall and rolls at a constant speed.

Roy gets to a position of 6 meters in a time of 2 seconds. How much is his velocity

for that time?

At the 6-m position, Roy then activates the fire extinguisher and speeds up. He ends

up at a position of 14.25 meters with a velocity of 3.5 m/sec. What was Roy’s

Acceleration?

How long did Roy accelerate?

Projectile motion

Describe:

The difference between vertical velocity and a horizontal velocity:

What “magic” numbers are and when/why to use them:

How to solve for time with an initial velocity that is not zero (toss-up):

Equations:

agravity (acceleration)=

units:

(y) displacement=

or ∆y =

or ∆y =

horizontal displacement (vconstant)=

When to use:

PRACTICE Problems:

A person kicks a ball straight up with an initial velocity of 50 m/sec.

How long does it take for the ball to reach its highest point?

How high did the ball go?

What is the final velocity of the ball when it hits the ground (the answer is not zero!)

Homer Andretti is driving recklessly (again). He’s going 40 m/sec (that’s like 100 mph!) on a road with a

cliff, he swerves to keep from hitting a woodchuck, and careens off of the road which is 200 m high.

When does the driver crash on the ground below?

How far from the cliff does the driver splat on ground below?

How much is the vertical velocity when the driver splats on the ground below?

Plot homer’s trip off the cliff on a separate piece of graph paper.

Forces and Special Forces

Equations:

Force total = Force centripetal =

units:

Force of gravity (wt)= acceleration centripetal =

Net Force= velocity tangential =

PRACTICE Problems:

Two people pull a 300 kg block. One person pulls with 700 Newton’s South while the other pulls with 900

Newton’s West.

How much is the Net Force acting on the block motion?

How much is the acceleration of the block, in the direction of its motion?

Pancho & Roy Blues get into an elevator at the ground floor. Pancho has a mass of 82 kg and is standing

on a bathroom scale. He gets into an elevator on the ground floor with a bathroom scale. The elevator

is at rest.

How much is Pancho’s Force of gravity?

The elevator zips him up and the scale on which he’s standing reads 1620N. Draw the free body

diagram for Pancho.

How much is the TOTAL Force on Pancho?

How much is Pancho’s acceleration?

This acceleration lasts 7 seconds. With how much velocity is Pancho going?

Gladys is just as crazy as Roy – she is taking a flying leap out of a plane! At least she has a parachute… and an

atmosphere! In each of the frames below, draw the free-body diagram to determine the Total Force (FTOT) on

Gladys as well as her acceleration. Gladys has a mass of 80 kg.

A 70 kg box is on top of a 150 kg box and the system is at rest.

Draw Free Body Diagrams for both boxes.

Label each force vector and pay attention to relative sizes of vectors.

Circle the 3rd Law Force Pair.

A person is swinging a ball around on a string. The person must use a force of 32.5 N to make the 1.3 kg

ball swing around a circle of radius 4 m.

How fast is the ball going?

How much is the acceleration of the ball?

Draw a free body diagram including all vectors.

Momentum

Equations:

impulse=

units:

(p) momentum=

units=

Bouncy collisions: Sticky collisions:

When to use:

PRACTICE Problems:

A Bean Burrito Especial has a mass of 2 kg and is traveling at 25 m/sec. A Chalupa has a mass of 3 kg and

traveling straight toward the Bean Burrito Especial with a velocity of –18 m/sec. After they experience a

bouncy collision, the Bean Burrito is moving at -26.6 m/sec. Fill in the known and unknown variables

below, and finally solve for the Chalupa’s final velocity.

mb= Vbi= Vbf = Mc= Vci= Vcf=

Pbi = Pci = Pbf = Pcf=

Now calculate the final velocity of the Bean Burrito Especial and the Chalupa if they stick together upon

impact.

mb= Vbi= Vbf = Mc= Vci= Vcf=

Pbi = Pci = Pbf = Pcf=