U2 Conservation Energy - Fill the blank

m = 10 kg

k = 40 Nm

∆x = 2 m

The energy stored according to the picture is = (include the symbol of the unit)

Answer explanation

Ep = 1/2 k (∆x)²

Ep = 1/2 (40) (2)²

Ep = 20 (4)

Ep = 80 Joules

Ep = 80J

What is the initial energy (initial energies)?

• GPE

• GPE + Ek

• Ek

• GPE + Ep

m = 2 kg

g ≈ 10

What is the initial GPE?

m = 2 kg

g ≈ 10

What is the initial KE?

Answer explanation

KE = 1/2 (2kg) (4.0)²

KE = 1 (16)

KE = 16 Joules

KE = 16J

m = 2 kg

g ≈ 10

What is the initial energy in total?

Answer explanation

Initial Energy = GPE + KE

Initial Energy = 20 + 16

Initial Energy = 36J

m = 2 kg

g ≈ 10

What is the final energy just before hitting the ground?

Answer explanation

Initial Energy = GPE + KE

Initial Energy = 20 + 16

Initial Energy = 36J

Final Energy = 36J

The object started at A but stopped at C due to the friction between B and C.

Work done by friction = 80J

What is the initial energy?

Answer explanation

Energy cannot be created nor destroy.

Initial energy = final energy

The object started at A but stopped at C due to the friction between B and C.

Work done by friction = 80J

m = 10kg

What is the kinetic energy at B?

Answer explanation

Energy cannot be created nor destroy.

Initial energy = final energy

The object started at A but stopped at C due to the friction between B and C.

Work done by friction = 80J

distance from B to C = 20m

What is the friction force from B to C? (include units)

Answer explanation

Work Done = F • s

80J = Ff • 20m

Ff = 4N