Work and Energy

Question 1

What is work?

Answer 1

work occurs when a force causes the displacement (change in position) of an object; if the object has not moved (in the same direction as the force), work was NOT done by the force

Question 2

What is acceleration?

Answer 2

how much an object is speeding up or slowing down (the rate at which an object’s velocity changes with respect to time)

Question 3

What is displacement?

Answer 3

a change in position (direction matters)

example: two steps forward and two steps back is a displacement of 0 steps

Question 4

What is distance?

Answer 4

total travel (direction does NOT matter)
example: two steps forward and two steps back is a distance of 4 steps

Question 5

What is the acceleration due to gravity on Earth (g)?

Answer 5

g = 9.8 m/s² (sometimes rounded to 10 m/s²)

Question 6

What is the formula for acceleration?

Answer 6

acceleration = change in velocity ÷ time

Question 7

What is the formula for kinetic energy (KE)?

Answer 7

kinetic energy = ½ ⋅ mass ⋅ velocity²

KE = ½mv²

Question 8

What is the formula for mechanical energy?

Answer 8

mechanical energy = potential energy + kinetic energy

ME = PE + KE

Question 9

What is the formula for momentum?

Answer 9

momentum = mass ⋅ velocity
p = mv

Question 10

What is the formula for potential energy (PE) due to gravity?

Answer 10

potential energy = mass × acceleration due to gravity × height
PE = mgh

Question 11

What is the formula for power?

Answer 11

power = work ÷ time
P = W/t
units: watts = joules ÷ seconds

Question 12

What is the formula for speed?

Answer 12

speed = distance ÷ time

direction does NOT matter

Question 13

What is the formula for velocity?

Answer 13

velocity = displacement ÷ time
v = d/t
(direction matters)

Question 14

What is the formula for work?

Answer 14

work = force ⋅ distance
W = Fd
(joules = Newtons ⋅ meters)

Question 15

What is the SI unit for acceleration?

Answer 15

meters per second² (m/s²)

Question 16

What is the SI unit for distance or displacement?

Answer 16

meter (m)

Question 17

What is the SI unit for energy?

Answer 17

joule (J)

Question 18

What is the SI unit for force?

Answer 18

Newton (N)

Question 19

What is the SI unit for power?

Answer 19

watt (W)

Question 20

What is the SI unit for time?

Answer 20

seconds (s)

Question 21

What is the SI unit for velocity?

Answer 21

meters per second (m/s)

Question 22

What is the SI unit for work?

Answer 22

joule (J)

Question 23

What is the work-energy theorem?

Answer 23

Work done by an external force on an object changes the object’s mechanical energy, so:

work = change in potential energy
(the object was raised or lowered)

AND/OR

work = change in kinetic energy
(the object’s velocity increased or decreased)

Question 24

What is velocity?

Answer 24

how fast an object is moving (the rate at which an object’s position changes with respect to time); if an object is not moving, its velocity is 0 m/s

Question 25

What is power?

Answer 25

the rate at which work is done with respect to time

Question 26

What is the formula for impulse?

Answer 26

impulse = force ⋅ time
impulse = mass ⋅ change in velocity

Question 27

What is kinetic energy?

Answer 27

the energy of motion; if an object is not moving, its kinetic energy is 0 joules

Question 28

What is potential energy due to gravity?

Answer 28

the energy stored because of an object’s position above the ground; if an object is on the ground, its potential energy is 0 joules