CSLB General Building (B) — All Questions
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Which simple machine is a doorknob an example of?
- a.Wheel and axle✓
- b.Pulley
- c.Wedge
- d.Inclined plane
A doorknob turns a shaft, so the large knob and thin spindle form a wheel and axle. Turning the larger wheel produces a stronger turning force on the smaller axle.
A lever is used mainly to:
- a.store electricity
- b.increase force✓
- c.reduce weight
- d.produce heat
A lever multiplies the force applied to it, making it easier to move a load. Placing the fulcrum closer to the load increases this mechanical advantage.
If two people push on a box from opposite sides with equal force, the box will:
- a.move toward the stronger side
- b.spin in place
- c.stay still✓
- d.speed up
Equal and opposite forces cancel out, producing a net force of zero. With no net force, the box remains at rest, an example of balanced forces.
A pulley system is used to:
- a.create electricity
- b.reduce friction to zero
- c.increase temperature
- d.change the direction of a force✓
A single fixed pulley lets you pull down to lift a load up, changing the direction of the applied force. Adding more pulleys can also reduce the effort needed.
Which of these is an example of an inclined plane?
- a.A ramp✓
- b.A wheelbarrow
- c.A seesaw
- d.A ceiling fan
A ramp is a flat surface set at an angle, which is the definition of an inclined plane. It makes raising a load easier by spreading the effort over a longer distance.
The force that opposes the motion of two surfaces sliding against each other is:
- a.gravity
- b.friction✓
- c.tension
- d.buoyancy
Friction acts between contacting surfaces and resists their relative sliding motion. Rougher surfaces generally produce more friction than smooth ones.
In a class-one lever, the fulcrum is located:
- a.at the load end only
- b.at the effort end only
- c.between the effort and the load✓
- d.outside the lever
A class-one lever, such as a seesaw, has its fulcrum between the effort and the load. A crowbar prying a nail is another common example.
Two gears mesh together. If the driving gear turns clockwise, the driven gear will turn:
- a.clockwise
- b.in both directions
- c.not at all
- d.counterclockwise✓
When two gears mesh directly, they turn in opposite directions. So if the driving gear turns clockwise, the meshed driven gear turns counterclockwise.
A smaller gear driving a larger gear will cause the larger gear to turn:
- a.more slowly✓
- b.faster
- c.at the same speed
- d.backward only
A small gear driving a large gear reduces speed but increases turning force, or torque. The larger gear turns more slowly because it has more teeth to move per revolution.
Which object has the most gravitational potential energy?
- a.A rock at the bottom of a hill
- b.A rock at the top of a hill✓
- c.A rock rolling on flat ground
- d.A rock resting in a valley
Gravitational potential energy increases with height. A rock at the top of a hill is highest, so it has the greatest stored energy ready to convert to motion.
Increasing the length of a lever's effort arm will:
- a.decrease the force output
- b.have no effect
- c.increase the mechanical advantage✓
- d.reduce the load
A longer effort arm gives more leverage, increasing the mechanical advantage. This lets a smaller effort force lift a larger load.
Air pressure is greatest at:
- a.the top of a mountain
- b.high in the atmosphere
- c.the edge of space
- d.sea level✓
Air pressure is highest at sea level because the full weight of the atmosphere presses down there. Pressure decreases with altitude as less air remains above.
A wedge is used to:
- a.split or separate objects✓
- b.lift objects with a rope
- c.store rotational energy
- d.reduce electrical current
A wedge is a moving inclined plane that concentrates force to split or separate materials. An axe head and a knife blade are common wedges.
When a compressed spring is released, the stored energy is converted mainly into:
- a.heat only
- b.motion✓
- c.electricity
- d.sound only
A compressed spring stores elastic potential energy. When released, that energy is converted mainly into kinetic energy, causing the spring or an attached object to move.