Mixed Deck — All WTMA Topics Flashcards

Two identical balls are dropped from different heights. Ball A is dropped from 10 feet; Ball B from 20 feet. Compare their speeds just before hitting the ground.

Answer: Ball B is about 1.4 times faster than Ball A

Speed is proportional to the square root of height (v = √(2gh)), so doubling height increases speed by √2 ≈ 1.4 times.

In a simple electrical circuit, if the voltage is doubled and the resistance remains constant, what happens to the current?

Answer: It doubles.

According to Ohm's Law (V=IR, or I=V/R), current (I) is directly proportional to voltage (V) and inversely proportional to resistance (R). If the voltage is doubled while resistance stays the same, the current must also double to maintain the relationship.

A bicycle rider coasts down a hill and gains speed. Which energy conversion is occurring?

Answer: Gravitational potential to kinetic

As the rider descends, gravitational potential energy converts into kinetic energy, increasing speed.

Which material is the BEST conductor of electricity?

Answer: Copper

Copper has very low electrical resistance and is one of the best practical conductors used in wiring.

A motor lifts a 500 lb load 10 feet in 5 seconds. What is the power output?

Answer: 1,000 ft-lb/s

Power = (Force × Distance) / Time = (500 × 10) / 5 = 1,000 ft-lb/s.

Two identical metal blocks, A and B, are painted different colors. Block A is painted matte black, and Block B is painted shiny silver. Both are placed in direct sunlight. Which block will heat up faster?

Answer: Block A, because dark, matte surfaces are better absorbers of radiant heat.

Dark, matte surfaces are excellent absorbers of radiant energy, while shiny, light-colored surfaces are good reflectors. The matte black surface of Block A will absorb more of the sun's radiation compared to the shiny silver surface of Block B, causing it to heat up more quickly.

A 6-tooth sprocket drives a 24-tooth sprocket. The driven sprocket rotates at what fraction of the driver's speed?

Answer: One-quarter the speed

Speed ratio for chain drives = driver teeth / driven teeth = 6/24 = 1/4, so the driven sprocket turns at one-quarter the driver's speed.

Which of the following actions would increase the kinetic friction between a moving sled and the snowy ground?

Answer: Adding more weight to the sled.

The force of kinetic friction is calculated as the product of the coefficient of kinetic friction and the normal force. The normal force is equal to the weight of the sled (mass times gravity). By adding more weight to the sled, you increase the normal force, which in turn increases the force of kinetic friction.

Which of the following best describes mechanical advantage gained from a wheel-and-axle system?

Answer: Turning the larger wheel requires less force to overcome load on the smaller axle

A large wheel provides mechanical advantage by allowing a small input force over a large radius to overcome a larger load at the smaller axle radius.

What is the formula for calculating work?

Answer: Work = Force × Distance

In physics, work is defined as the energy transferred to or from an object by applying a force that causes displacement. The formula for calculating work is Work = Force × Distance (W = Fd). This means that work is done only when a force causes an object to move over a certain distance in the direction of the force.

What is the ratio of the pulling force F to the load L if the weight of each pulley is equal to the load? (F / L =?)

Answer: 1

In an ideal pulley system, the ratio of the pulling force (F) to the load (L) is equal to 1 divided by the mechanical advantage (MA). If the ratio F/L is 1, it implies that the pulling force is equal to the load. This scenario typically occurs with a single fixed pulley, which only changes the direction of the force but does not provide any mechanical advantage in terms of reducing the force required to lift the load. The information about the weight of each pulley is a distractor for this ideal scenario.

A hydraulic lift uses two pistons. Piston A has a surface area of 2 square inches, and Piston B has a surface area of 10 square inches. If a force of 50 pounds is applied to Piston A, what is the maximum lifting force that can be generated by Piston B?

Answer: 250 pounds

This question applies Pascal's Law, which states that pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and the walls of the containing vessel. The pressure (P) is Force (F) divided by Area (A), so P = F/A. The pressure on Piston A is 50 lbs / 2 in² = 25 psi. This pressure is transmitted to Piston B. The force on Piston B is P × Area B = 25 psi × 10 in² = 250 pounds.

Which class of lever has the fulcrum located between the effort and the load?

Answer: First class

A first-class lever has the fulcrum between the effort and the load, like a seesaw.

What is the primary advantage of a V-belt over a flat belt for power transmission?

Answer: Higher friction grip and reduced slipping

The wedging action of a V-belt seated in its groove creates more friction contact than a flat belt, significantly reducing slippage under load.

To reverse the direction of rotation of a driven pulley in a belt drive, you would use a:

Answer: Crossed belt drive

A crossed belt drive reverses the direction of the driven pulley by crossing the belt between the two pulleys before it wraps around the driven side.

Which property of a fluid describes its resistance to flow?

Answer: Viscosity

Viscosity is the measure of a fluid's internal friction and resistance to flow.

A block is sliding down a frictionless ramp. Which of the following forces is responsible for its acceleration down the ramp?

Answer: The component of gravity parallel to the ramp's surface.

The force of gravity acts vertically downwards. On an inclined plane, this force can be resolved into two components: one perpendicular to the ramp and one parallel to it. The perpendicular component is balanced by the normal force. The parallel component is unbalanced (since there is no friction) and pulls the object down the ramp, causing it to accelerate.

Imagine you are using a crowbar to lift a heavy rock. You place a small stone under the crowbar to act as a fulcrum. The rock is the load, and you push down on the end of the crowbar. This is an example of which class of lever?

Answer: First-Class Lever

In a first-class lever, the fulcrum is located between the effort (your push) and the load (the rock). A seesaw and a crowbar used in this manner are classic examples of first-class levers.

What is the primary purpose of a tap wrench?

Answer: Cutting internal threads in a hole

A tap wrench holds and turns a tap to cut internal (female) threads inside a drilled hole.

A pump moves 200 gallons of water per minute to a height of 50 feet. If water weighs 8.34 lbs/gallon, approximately how much power is needed (in ft-lb/min)?

Answer: 83,400 ft-lb/min

Power = (200 gal/min × 8.34 lb/gal × 50 ft) = 83,400 ft-lb/min.