Work and Energy5. What is a force?

a. change in speed over timeb. the tendency to resist change in

motionc. a push or pulld. apparent weightlessness

Work and Energy5. What is a force?

a. change in speed over timeb. the tendency to resist change in

motionc. a push or pulld. apparent weightlessness

Work and Energy9. What is the result of a net force

acting on an object? a. the object will accelerateb. the object remain motionlessc. the object’s velocity will not changed. inertia is greater than net forces

Work and Energy9. What is the result of a net force

acting on an object? a. the object will accelerateb. the object remain motionlessc. the object’s velocity will not changed. inertia is greater than net forces

Work and EnergyWhich of the following does NOT

represent work being done.a. You lift a 4 kg box 1.5 m to the table.b. You pull a wagon 10 meters.c. You hold the door open for your mom.d. You push a desk across the floor.

Work and EnergyWhich of the following does NOT

represent work being done.a. You lift a 4 kg box 1.5 m to the table.b. You pull a wagon 10 meters.c. You hold the door open for your mom.

Why?d. You push a desk across the floor.

Work and EnergyWhich of the following does NOT

represent work being done.c. You hold the door open for your

mom. Why?Even though you apply force to to keep

the door open, the door does not move.

Work and EnergyThe amount of work done in a

specified amount of time is calleda. joulesb. resistancec. powerd. Mechanical advantage

Work and EnergyThe amount of work done in a

specified amount of time is calleda. joulesb. resistancec. powerd. Mechanical advantage

Work and EnergyAn object that is only acting under the

influence of gravity is ___________a. deceleratingb. in free fallc. stationaryd. weightless

Work and EnergyAn object that is only acting under the

influence of gravity is ___________a. deceleratingb. in free fallc. stationaryd. weightless

Work and EnergyFor every force there is an equal and

opposite reaction force is a. Newton's 1st Law of Motion

b. Newton's 2nd of Motionc. Newton's 3rd Law of Motiond. Newton's 4th Law of Motion

Work and EnergyFor every force there is an equal and

opposite reaction force is a. Newton's 1st Law of Motionb. Newton's 2nd of Motionc. Newton's 3rd Law of Motiond. Newton's 4th Law of Motion

Work and EnergyWhat is the gravitational acceleration

constant on earth?a. 9.8 m/sb. 98 m/sc. 9.8 m/s2

d. 982 mph

Work and EnergyWhat is the gravitational acceleration

constant on earth?a. 9.8 m/sb. 98 m/sc. 9.8 m/s2

d. 982 mph

Work and EnergyWhich state of matter is completely compressed, retains its shape, and represents the lowest form of kinetic energy among its molecules?

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Work and EnergyWhich state of matter is completely compressed, retains its shape, and represents the lowest form of kinetic energy among its molecules?

solids

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Work and EnergyWhat is the equation for calculating kinetic

energy?

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Work and EnergyWhat is the equation for calculating kinetic

energy?KE = ½ mv2

OR

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2mvKE=2

Work and EnergyKinetic energy is expressed in what units?

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Work and EnergyEnergy is measured in what units?

JoulesJ

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Work and EnergyWhat is the kinetic energy of a 5kg object

traveling at 10m/s?

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Work and EnergyWhat is the kinetic energy of a 5kg object

traveling at 10m/s?KE = ½ mv2

KE = 5kg x (10m/s)2

2= 250 J

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Work and EnergyWhat is the equation for calculating

gravitational potential energy?

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Work and EnergyWhat is the equation for calculating

potential energy? PE = mgh

What do the letters stand for?

Work and EnergyWhat is the equation for calculating

potential energy? PE = mgh

What do the letters stand for?m = mass g = gravity (9.8m/s2)

h = height of the object in m

Work and EnergyA 1.5 kg coconut hangs in a palm tree?

How much gravitational potential energy does the coconut have if the tree is 15 meters tall?

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Work and EnergyA 1.5 kg coconut hangs in a palm tree?

How much gravitational potential energy does the coconut have if the tree is 15 meters tall?

PE = mgh= (1.5 kg)(9.8m/s2)(15 m)

220 J

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Work and EnergyA rollercoaster car with a mass of 500 kg

has 600 J of potential energy. How tall is the rollercoaster?

PE = mgh so = 600 kJ/(9.8m/s2 x 500kg)

= 122 m

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PE hgm

Work and EnergyWhat is the mechanical energy of a 40 kg

child swinging at the moment her velocity is 20 m/s and she is 2 m off of the ground?

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Work and EnergyWhat is the mechanical energy of a 40 kg

child swinging at the moment her velocity is 20 m/s and she is 2 m off of the ground?

Hint: Mechanical Energy = KE + PE Calculate each and sum.

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Work and EnergyCalculate the mechanical energy of a 40 kg

child swinging at the moment her velocity is 20 m/s and she is 2 m off of the ground?

Hint: Mechanical Energy = KE + PE

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2

2mv mgh

Work and EnergyCalculate the mechanical energy of a 40 kg

child swinging at the moment her velocity is 20 m/s and she is 2 m off of the ground?

Hint: Mechanical Energy = KE + PE

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2

2

2

40 2040 9.8 2 8784

2

mkg s mkg m Js

Work and EnergyWhat is the mechanical energy of a 40 kg

child swinging at the moment her velocity is 20 m/s and she is 2 m off of the ground?

PE = mgh so = 600 kJ/(9.8m/s2 x 500kg)

= 122 m

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PE hgm