Quiz #1

The sketch shows a painter's scaffold in mechanical equilibrium. The person in the middle weighs 500 N, and the tensions in each rope are 400 N. What is the weight of the scaffold?

W = 300 N

Lucy Lightfoot stands with one foot on one bathroom scale and her other foot on a second bathroom scale. Each scale reads 355 N . What is Lucy's weight?

W = 710 N

A block pulled to the left with 15 N and to the right with 5 N at the same time experiences a net force of a) 10 N. b) 20 N. c) 15 N. d) 5 N.

a) 10 N.

When you stand at rest on a pair of bathroom scales, the reading on each scale a) add up to equal your weight. b) equals your weight. c) is half your weight.

a) add up to equal your weight.

When a rocket ship gaining speed in outer space runs out of fuel, it a) no longer gains speed. b) gains speed for a short time, slows down, and eventually stops. c) gains speed for a short time, then slows down to a constant velocity.

a) no longer gains speed.

A pair of wires support a heavy painting. Tension in the wires is greater when they are a) not vertical. b) vertical. c) the same regardless of the wire orientation. d) none of the above

a) not vertical.

Inertia is defined as a a) property of matter. b) change in motion. c) force. d) none of the above

a) property of matter.

The net force acting on an insect falling downward at constant velocity is a) zero. b) upward air resistance. c) the weight of the insect. d) none of the above

a) zero.

A pair of 10-N vectors at right angles to each other has a resultant of about a) 20 N. b) 14 N. c) 10 N. d) none of the above

b) 14 N.

A hockey puck sliding at constant velocity across the ice is a) is nowhere near being in equilibrium. b) in equilibrium. c) nearly in equilibrium. d) none of the above

b) in equilibrium.

While you are standing in the aisle of a bus, the driver suddenly makes a left turn. You lurch to the right due to a) an unbalanced force. b) your tendency to keep moving forward. c) an equilibrium challenge.

b) your tendency to keep moving forward.

If you toss a coin straight upward in train that gains speed while the coin is in the air, the coin will land a) as if you were at rest. b) in front of you. c) in back of you.

c) in back of you.

A sheet of paper can be quickly jerked beneath a container of milk without toppling, which best demonstrates a) the difference between force and mass. b) net force. c) inertia.

c) inertia.

An object in mechanical equilibrium is an object a) having no changes in velocity. b) moving with constant velocity. c) at rest. d) all of the above

d) all of the above

Galileo taught us that if you roll a ball along a level surface it will a) soon slow down due to its natural place. b) roll as long as its inertia nudges it along. c) soon roll in the opposite direction. d) keep rolling if friction is absent.

d) keep rolling if friction is absent.