Mechanical Comprehension · Practice test 7

Question 1Not answered

A lever has an effort arm of 10 inches and a resistance arm of 2 inches. What effort will lift a 200 pound load?

1. 1000 pounds
2. 100 pounds
3. 20 pounds
4. 40 pounds

Question 2Not answered

Seat belts matter in a sudden stop because

1. the car pushes the occupant backward as it stops
2. the occupant's body keeps moving forward after the car halts
3. gravity pulls the occupant toward the windscreen
4. the occupant becomes heavier during the impact

Question 3Not answered

How much work is done pushing a crate 4 metres with a force of 50 newtons?

1. 54 joules
2. 12.5 joules
3. 46 joules
4. 200 joules

Question 4Not answered

A machine does 600 joules of work in 3 seconds. What is its power output?

1. 1800 watts
2. 603 watts
3. 0.005 watts
4. 200 watts

Question 5Not answered

Two workers pull on a rope in exactly opposite directions with 150 newtons each. What is the net force on the rope?

1. 0 newtons
2. 300 newtons
3. 150 newtons
4. 75 newtons

Question 6Not answered

As a rock falls from a cliff, its energy is converted from

1. kinetic to potential
2. chemical to potential
3. kinetic to chemical
4. potential to kinetic

Question 7Not answered

No real machine reaches 100 percent efficiency because

1. some input energy is always lost to friction and heat
2. machines cannot multiply force without losses in size
3. the output force is always smaller than the input force
4. energy is destroyed as the machine operates

Question 8Not answered

How much work is done pushing a crate 8 metres across a floor with a steady force of 25 newtons?

1. 200 joules
2. 33 joules
3. 3.1 joules
4. 400 joules

Question 9Not answered

A single movable pulley, attached directly to the load with the rope's other end anchored above, has a mechanical advantage of about

1. 2
2. 1
3. 4
4. 0.5

Question 10Not answered

Two bevel gears meshed at a right angle are most useful for

1. converting rotary motion into straight-line motion
2. multiplying torque without changing speed at all
3. transmitting rotation between two shafts that are not parallel
4. preventing any rotation from being transmitted

Question 11Not answered

A force of 30 pounds is applied 2 feet from a pivot. How much torque does it produce?

1. 60 pound-feet
2. 15 pound-feet
3. 32 pound-feet
4. 28 pound-feet

Question 12Not answered

Doubling the diameter of a hydraulic piston, while keeping the force applied the same, will cause the pressure it produces to

1. double
2. decrease to one quarter of its original value
3. stay exactly the same
4. increase to four times its original value

Question 13Not answered

Lubrication reduces friction between two surfaces by

1. making both surfaces harder
2. holding them apart with a film of fluid
3. increasing the pressure between them
4. cooling them below room temperature

Question 14Not answered

To loosen a very tight bolt with less applied force, a mechanic should generally use a wrench that is

1. shorter, to increase the moment arm
2. the same length but made of a heavier material
3. length makes no difference to the torque produced
4. longer, to increase the moment arm

Question 15Not answered

Six rope sections support the load in a block and tackle. What effort lifts 600 pounds, ignoring friction?

1. 3600 pounds
2. 594 pounds
3. 100 pounds
4. 300 pounds

Question 16Not answered

A block and tackle lifts a load 2 metres using a system with mechanical advantage 5. How far must the effort end of the rope be pulled?

1. 2.5 metres
2. 0.4 metres
3. 10 metres
4. 2 metres

Question 17Not answered

According to Archimedes' principle, the buoyant force on a submerged object equals

1. the weight of the object itself
2. the volume of the object in cubic metres
3. the density of the fluid alone
4. the weight of the fluid the object displaces

Question 18Not answered

A machine that is 80 percent efficient delivers 400 joules of useful output. How much energy went in?

1. 320 joules
2. 480 joules
3. 500 joules
4. 420 joules

Question 19Not answered

One horsepower is defined as

1. 550 foot-pounds of work per second
2. 550 foot-pounds of work in total
3. 100 foot-pounds of work per second
4. the force one horse can pull

Question 20Not answered

A net force of 60 newtons accelerates a cart at 3 metres per second squared. What is the cart's mass?

1. 180 kilograms
2. 57 kilograms
3. 20 kilograms
4. 3 kilograms

Question 21Not answered

A cable supporting a hanging load is under

1. compression
2. shear
3. no stress at all
4. tension

Question 22Not answered

A check valve in a fluid system

1. permits flow in one direction only
2. regulates the pressure of the system
3. filters particles out of the fluid
4. measures the rate of the flow

Question 23Not answered

Newton's second law of motion connects

1. force, mass, and acceleration
2. work, energy, and time
3. pressure, area, and volume
4. torque, friction, and speed

Question 24Not answered

Compared to a stiff, brittle material, a material with high elasticity will

1. shatter immediately under any load
2. return to its original shape after being deformed within its elastic limit
3. permanently deform under the lightest touch
4. never break under any amount of force

Question 25Not answered

An I-beam cross section is shaped with wide flanges at the top and bottom connected by a thin web. This shape is efficient because

1. it uses the least material regardless of loading
2. the thin web alone carries all the bending load
3. most of the bending resistance comes from material far from the centre, where the flanges are
4. it eliminates the need for any support columns