Mechanical Comprehension · Practice test 8

Question 1Not answered

Acceleration is defined as the rate at which

1. velocity changes
2. distance is covered
3. force is applied
4. energy is used up

Question 2Not answered

The gravitational potential energy of a raised object depends on

1. its mass and its speed at that moment
2. its mass, the pull of gravity, and its height
3. its shape and the surface it rests on
4. how long it has been held at that height

Question 3Not answered

Water flowing through a pipe that narrows will

1. slow down as it passes through the narrow section
2. keep exactly the same speed throughout
3. stop flowing once the pipe narrows
4. speed up as it passes through the narrow section

Question 4Not answered

One horsepower is equal to about how many watts?

1. 746 watts
2. 1000 watts
3. 100 watts
4. 60 watts

Question 5Not answered

The chief benefit of a single fixed pulley is that it

1. halves the effort needed to lift the load
2. changes the direction in which the effort is applied
3. doubles the distance the load can be raised
4. removes friction from the lifting system

Question 6Not answered

A screw jack has a handle 40 centimetres long and a thread pitch of 0.5 centimetres per turn. What is its approximate ideal mechanical advantage?

1. about 80
2. about 20
3. about 251
4. about 503

Question 7Not answered

Compared to lifting a heavy box straight up, pushing it up a long, gently sloped ramp requires

1. more force but a shorter distance of travel
2. the same force and the same distance
3. no force at all, since ramps are frictionless
4. less force but a longer distance of travel

Question 8Not answered

A hydraulic piston with an area of 8 square centimetres supports a load that creates 40 newtons of force. What pressure, in newtons per square centimetre, is in the fluid?

1. 320 newtons per square centimetre
2. 5 newtons per square centimetre
3. 0.2 newtons per square centimetre
4. 48 newtons per square centimetre

Question 9Not answered

Compared with a belt drive, a chain drive

1. runs more quietly under heavy load
2. needs no lubrication of any kind
3. can transmit motion over greater distances
4. does not slip, so the ratio stays exact

Question 10Not answered

A rack-and-pinion mechanism, such as in a car's steering system, converts

1. rotary motion of the pinion into straight-line motion of the rack
2. straight-line motion only, with no rotary parts
3. hydraulic pressure directly into torque
4. electrical energy into mechanical energy

Question 11Not answered

Hooke's law states that the distance a spring stretches is

1. independent of the force applied to it
2. proportional to the square of the force
3. determined only by the spring's length
4. proportional to the force applied to it

Question 12Not answered

Turning the large steering wheel of a ship to move a much smaller rudder shaft is a practical use of which simple machine?

1. a lever of the third class
2. a wedge
3. a wheel and axle
4. a pulley

Question 13Not answered

A pair of scissor blades cutting through paper apply mainly which type of stress to the paper?

1. tension
2. compression
3. shear
4. torsion

Question 14Not answered

Adding oil between two metal surfaces that slide against each other primarily works by

1. increasing the roughness of both surfaces
2. increasing the normal force between the surfaces
3. chemically dissolving the metal surfaces
4. keeping the surfaces separated so they do not grind directly against each other

Question 15Not answered

Which statement matches the first of Newton's laws of motion?

1. accelerates in proportion to the force applied to it
2. keeps doing what it is doing until a force acts on it
3. pushes back with equal force on whatever pushes it
4. falls at a rate that depends on how heavy it is

Question 16Not answered

A ramp 12 metres long rises to a height of 3 metres. What is its ideal mechanical advantage?

1. 0.25
2. 9
3. 4
4. 15

Question 17Not answered

A worm gear meshing with a worm wheel is most valued in machinery because it

1. always speeds up rotation dramatically
2. has no sliding friction at all
3. provides a large speed reduction and normally cannot be back-driven
4. is used only to reverse rotation direction

Question 18Not answered

Shear stress is the kind of force that tends to make parts of a material

1. be squeezed together
2. be pulled apart lengthwise
3. slide past one another
4. twist about a central axis

Question 19Not answered

Compared to a gear train, a belt and pulley drive between two shafts that are far apart has the advantage of

1. never slipping under heavy load
2. always being more precise than gears
3. not requiring the shafts to be close together or precisely aligned
4. requiring no maintenance ever

Question 20Not answered

A sign is held up by two ropes pulling upward at equal angles. If one rope suddenly goes slack, what happens to the sign?

1. it stays perfectly still, since one rope is enough
2. it rises upward
3. it swings and drops toward the side of the slack rope
4. it becomes heavier

Question 21Not answered

What is the main purpose of an idler gear placed between a drive gear and a driven gear of the same size?

1. to double the speed of the driven gear
2. to reduce the torque delivered to the driven gear
3. to make the driven gear turn the same direction as the drive gear, without changing speed
4. to lock the gear train so nothing can rotate

Question 22Not answered

Compared with lifting a load directly, a single movable pulley lets you

1. use half the force and pull the same rope
2. use half the force but pull twice the rope
3. use the same force but pull half the rope
4. use a quarter of the force over the same distance

Question 23Not answered

In a hydraulic jack, the small piston compared with the large one must move

1. a shorter distance
2. a greater distance
3. exactly the same distance
4. a distance set by the fluid used

Question 24Not answered

A gear reduction of 4 to 1 (output turns 4 times slower than input) will make the output shaft's torque, compared to the input shaft's torque,

1. about 4 times greater
2. about 4 times smaller
3. unchanged
4. impossible to determine from the ratio alone

Question 25Not answered

A ship built of steel floats because

1. steel is lighter than water for its size
2. its hull shape displaces more water than the ship weighs
3. the engines push it upward while running
4. salt water is heavier than the steel hull