SME
Grade 8 Science · Problem type
Kinetic energy: mass and speed
Use this for “What has a bigger effect on kinetic energy, doubling the speed or doubling the mass?”
Table
Speed (v)
(m/s)
Kinetic energy (KE)
(J)
This is an example. Type your own values to start a new problem.
KE (J)
=
1
2
×
m (kg)
×
(
v (m/s)
)
2
Formulas
KE
=
1
2
×
m
×
v
2
(kinetic
energy
=
1/2
×
mass
×
speed²)
100
=
1
2
×
2 ×
10
2
Assumptions
•
Kinetic energy is the energy of moving: 1/2 × m × v².
•
Twice the mass, twice the energy. Twice the speed, four times the energy, because the speed is squared.
•
A moving bat at 30 m/s carries 9 times the energy it has at 10 m/s: speed matters most in a collision.
Step-by-step
WE KNOW
m = 2 kg (mass), v = 10 m/s (speed)
FIND
kinetic energy (KE)
Step 1 · Find kinetic energy (KE)
Use KE = 1/2 × m × v² (kinetic energy = 1/2 × mass × speed²)
Half the mass times the speed squared.
KE
=
1
2
×
2 ×
10
2
KE
=
1
2
×
2
×
100
KE = 1 × 100
KE = 100 J
Check
Put the numbers back in. Both sides should match.
100
=
1
2
×
2 ×
10
2
✓
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.