Union Test Prep Mechanical Comprehension Part 1

What is matter?

anything that has mass and takes up space.

What is mass?

the amount of matter in any object and it is not dependent on gravity.

What is force resonsiblie for?

the interactions between two or more objects.

IS force a vector aor scalar quantity?

They are vector qunaitities, possessing magnitude and a direction

Force can be thoguh of as….

“pushes” or “pulls”

When an object experiences no acceleration what is the sum of the forces acting on the object?

Zero

What is gravity?

the force of attraction acting between two masses.

What is the formula for gravity?

where G is the universal gravitational constant,m1 is the first mass, m2 is the second mass, and r represents the distance between the centers of the masses. The force of gravity is only attractive.

Wha is this formual for?

Gravity

Why do dropped objects fall to the ground?

Objects fall because Earth’s gravity pulls them downward.

What is friction?

the force that opposes an object in motion

Friction is always opposite to the….

direction of motion.

hy does friction occur?

It arises from microscopic interactions between surfaces, where tiny irregularities and forces between materials resist movement.

What are the three types of energy in a system with friction?

• Potential energy (stored energy)

• Kinetic energy (energy of motion)

• Work done by friction (energy lost as heat)

How does friction affect energy?

Friction removes mechanical energy by converting it into heat.

What happens to a block sliding down a ramp?

The block’s potential energy changes into kinetic energy, while friction converts some energy into heat.

What is the formula for finding the ttoal energy in the system?

Potential Energy + Kinetic Energy + Work Done by Friction

What is compression?

A pushing force that squeezes an object inward from opposite sides.

What is tension?

A pulling force that stretches or pulls an object. In addition, tension is measured in Newtons.

What is Newton’s First Law of Motion?

An object will stay at rest or keep moving unless an outside force acts on it.

This is called inertia.

What is Newton’s Second Law of Motion?

The more force applied to an object, the more it accelerates.

The more mass an object has, the less it accelerates when the same force is applied.

What is Newton’s Second Law formula?

F = ma

What is Newton’s Third Law of Motion?

For every action, there is an equal and opposite reaction.

When one object pushes on another, the second object pushes back with equal force in the opposite direction.

What is inertia?

an object's tendency to resist a change in its motion.

What is air pressure?

the weight of air pushing on an area.

Why is air pressure greater closer to Earth's surface?

There is more air above you near Earth's surface, so the weight of the air pushing down is greater.

How does water pressure change with depth?

Water pressure increases as you go deeper because there is more water above you pushing down.

How does a hydraulic lift work?

A hydraulic lift uses fluid pressure to transfer force, allowing a small force to lift a heavier object.

Why can hydraulic systems transfer force?

Hydraulic systems use incompressible fluids, meaning the fluid cannot be easily compressed, so force is transferred through the fluid.

What is the relationship between the two cylinders in a hydraulic system?

Because the fluid cannot be compressed, the fluid transfers the force from one cylinder to the other.

The relationship is:

A1 x D1 = A2 X D2

What is the mechanical advantage relationship in a hydraulic system?

• D₁, D₂ = distance each cylinder moves

• A₁, A₂ = cross-sectional area of each cylinder

How do you find the amount of fluid added or removed?

Amount = Rate x Time

How do you find how much fluid is left in a tank when it is filling and emptying?

Final Amount = Starting Amount + Inflow - Outflow

What is torque?

a twisting force that makes an object rotate.

Wht is the formual for Torque?

t = rFsin(theta)

What is work in physics?

Work happens when a force moves an object a certain distance.

What is needed in order for work to be done?

Force and Moveent

What is the formula for work?

W = F x D

When is work positive?

Force and movement are in the same direction.

When is work enegative?

Force and movement are in opposite directions.

What are the common units for force?

Newtons (N)

What are the common units for distance?

Meters (m)

What are the common units for work?

Joules (J)

What is 1 Joule equal to?

1 Joule = 1 Newton x 1 meter

What is energy?

Energy is the ability to do work. All energy ican be used to perform wkr.

What is the formula for total mechanical energy?

Etotal = PE + KE

What is the total energy formula when an external (nonconservative) force acts on an object?

E (total) = PE + KE + W (external)

• PE = Potential Energy (stored energy)

• KE = Kinetic Energy (motion energy)

• W (external)​ = Work done by an outside force

What is kinetic energy?

the energy an object has because it is moving.

What is the formula for kinetic energy?

KE = ½ mv²

What is the work-energy theorem?

The work done on an object equals the change in its kinetic energy.

What is the formula for the work-energy theorem?

W = KE (final) = KE (initial)

What is potential energy?

stored energy based on an object's position.

What is the formula for potential energy?

PE = mgh

How does height affect gravitational potential energy?

The higher an object is, the more potential energy it has.
When the object is lowered, it loses potential energy.

What happens to potential energy when an object falls?

As an object falls, its potential energy changes into kinetic energy.

If air resistance/friction is ignored:

Loss of PE = Gain of KE

What type of energy does an object have at the top of its fall?

At the top, the object has mostly potential energy (PE) because it is at a high position.

What happens to energy while an object is falling?

The potential energy is being converted into kinetic energy.

What type of energy does an object have right before hitting the ground?

Right before hitting the ground, the object has mostly kinetic energy (KE) because it is moving at a high speed.

What is chemical energy?

energy stored in the bonds of molecules.

What is electric energy?

energy associated with moving electrons (electric current).

What is nuclear energy?

energy stored in the nucleus of an atom.

What is solar energy?

the light and heat energy from the Sun.

What is power?

Power is how quickly work is done.

What is the formula for power?

P = W/t

What is power measured in?

It is measured in watts (W)