A crane extends its boom farther outward while lifting the same load. What is the most important effect on stability?
Center of Gravity A The center of gravity of the system shifts outward B The load becomes lighter C The boom produces less leverage D The crane's wheelbase becomes wider
Extending the boom shifts the combined center of gravity outward and can reduce stability.
A box is sliding to the right across a rough floor. In which direction does friction on the box act?
Friction A To the right B To the left C Upward D Downward
Friction opposes relative motion, so it acts to the left.
When a hand-pump piston is pulled upward, pressure inside the cylinder decreases. Why can outside air enter through the intake valve?
Air Pressure A Outside air pressure is greater than cylinder pressure B Outside air pressure becomes zero C The piston removes all pressure differences D The valve pushes air inward mechanically
Air moves from higher pressure to lower pressure.
A shelf is most likely to support a heavy load without bending when its brackets are
Structural Support A placed close to the ends B placed together at the center C removed entirely D shorter than the shelf thickness
Supporting a shelf nearer its ends reduces unsupported span and bending.
Two directly meshing external spur gears turn in
Gears A opposite directions B the same direction C random directions D no direction unless one is larger
Directly meshing external gears rotate in opposite directions.
A small gear drives a larger gear. The larger driven gear normally turns
Gear Speed A slower B faster C at exactly the same speed D only clockwise
A larger driven gear turns more slowly than the smaller driving gear.
A lever has the fulcrum between the effort and the load. What class of lever is it?
Levers A First-class B Second-class C Third-class D Wheel-and-axle
A first-class lever has the fulcrum between effort and load.
A lever makes lifting easier when the effort arm is
Mechanical Advantage A longer than the load arm B shorter than the load arm C always equal to the load arm D not connected to the fulcrum
A longer effort arm increases mechanical advantage.
What is the main advantage of a single fixed pulley?
Pulley A It changes the direction of the applied force B It always cuts the force in half C It stores energy D It eliminates friction
A fixed pulley mainly changes the direction of force.
In an ideal pulley system, adding more rope segments that support the moving load generally
Pulley Systems A reduces the effort force needed B increases the load's weight C eliminates rope movement D makes the load move farther than the rope
More supporting rope segments increase ideal mechanical advantage.
Which action produces the greatest torque on a stuck bolt using the same force?
Torque A Push at the end of a longer wrench B Push near the bolt with a short wrench C Push directly along the handle toward the bolt D Use no lever arm
Torque increases with lever-arm length when force is applied effectively.
A hydraulic jack works mainly because pressure applied to a confined fluid is
Hydraulics A transmitted through the fluid B destroyed by the fluid C converted only into heat D limited to the smallest piston
Pascal's principle says pressure applied to a confined fluid is transmitted throughout it.
In an ideal hydraulic system, why can a larger output piston produce greater force?
Hydraulic Force A The same pressure acts over a larger area B The larger piston has less area C The fluid loses all pressure D Gravity stops acting
Force equals pressure times area, so greater area gives greater force.
A worker pushes a crate with 50 N of force through 4 m in the direction of the force. How much work is done?
Work A 12.5 J B 46 J C 200 J D 400 J
Work = force × distance = 50 × 4 = 200 joules.
Two machines perform the same amount of work. Machine A finishes in half the time of Machine B. Machine A has
Power A greater power B less power C the same power D zero power
Power is work divided by time, so less time means greater power.
A raised weight has energy because of its position. This is
Energy A gravitational potential energy B chemical energy C electrical resistance D thermal conductivity
A raised object stores gravitational potential energy.
Within its elastic range, a spring is stretched farther. What generally happens to the restoring force?
Springs A It increases B It decreases to zero C It reverses permanently D It becomes unrelated to stretch
Greater elastic deformation generally produces greater restoring force.
An object floats at rest in water when the buoyant force is
Buoyancy A equal to the object's weight B always zero C less than its weight D unrelated to displaced water
For floating equilibrium, buoyant force balances weight.
A metal rod is heated while free to move. What usually happens to its length?
Thermal Expansion A It increases slightly B It becomes zero C It always decreases D It cannot change
Most metals expand when heated.
One end of a metal spoon gets hot after the other end sits in hot soup. This is mainly
Heat Transfer A conduction B convection C radiation only D evaporation
Heat moving through solid metal is conduction.