If an object with a mass of #2 kg # changes speed from #9m/s# to #4 m/s#, by how much does its kinetic energy change?

Answer 1

Elena Albarran

#-65"J"#

The formula for kinetic energy is given by

#"KE" = 1/2 m v^2#

Initially, the kinetic energy is

#"KE"_"i" = 1/2 (2 "kg")(9 "m/s")^2#

#= 81 "J"#

In the end, the kinetic energy is

#"KE"_"f" = 1/2 (2 "kg")(4 "m/s")^2#

#= 16 "J"#

The change in kinetic energy is given by

#Delta "KE" = "KE"_"f" - ##"KE"_i#

#= 16 "J" - 81 "J"#

#= -65 "J"#

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Answer 2

Sebastian Acosta

To calculate the change in kinetic energy, you can use the formula:

ΔKE = ½ * m * (vf^2 - vi^2)

Where: ΔKE = change in kinetic energy m = mass of the object vf = final velocity vi = initial velocity

Substituting the given values:

m = 2 kg vf = 4 m/s vi = 9 m/s

ΔKE = ½ * 2 kg * ((4 m/s)^2 - (9 m/s)^2)

ΔKE = ½ * 2 kg * (16 m^2/s^2 - 81 m^2/s^2)

ΔKE = ½ * 2 kg * (-65 m^2/s^2)

ΔKE = -65 J

So, the kinetic energy decreases by 65 joules.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.