Work, Power, and Energy Oh my! Clicker Review 12/9/2013

Concept Questions Work is a form of energy. True False Question Answer Choices Work is a form of energy. True False Work is the energy “lost” by the entity that exerts the force on an object for a distance.

Concept Questions True False Answer Choices True False No. Joules are units of Work just like energy. Watts are the units of Power A Watt is the standard metric unit of work. What is the standard unit of work and Energy?

Concept Questions True False Power! Answer Choices True False Power! Work is a time- based quantity; it is dependent upon how fast a force displaces an object. What word should replace Work?

Concept Questions Question Answer Choices True False Why? No Displacement No Diagram Superman applies a force on a truck to prevent it from moving down a hill. This is an example of work being done.

Concept Questions Question Answer Choices True False Why? The movement is not in the same direction as the force. An upward force is applied to a bucket as it is carried 20 m across the yard. This is an example of work being done. F D

Concept Questions True False F D Answer Choices True False A force is applied by a chain to a roller coaster car to carry it up the hill of the first drop of the Shockwave ride. This is an example of work being done. F D

Concept Questions Question Answer Choices True False Vice versa. If two people do the same job, then they're doing the same amount of work. The person who does it fastest generates more power. If person A and person B do the same job but person B does it faster, then person A does more work but person B has more power.

Concept Questions Positive Work Negative Work No Work Answer Choices Rusty Nales uses a hammer to exert an applied force upon a stubborn nail to drive it into the wall. Positive Work Negative Work No Work Force diagram in same direction so is positive work F D

Concept Questions Gravitational Frictional Applied Answer Choices Which of the following is a non-conservative force? Gravitational Frictional Applied

Which of the following statements are true about mechanical energy? Concept Questions Question Answer Choices The total amount of mechanical energy of an object is the sum of its potential and the kinetic energy. Heat is a form of mechanical energy. The mechanical energy of an object is always conserved. When non-conservative forces do work, energy is transformed from kinetic to potential , but the total mechanical energy is conserved. Which of the following statements are true about mechanical energy?

Concept Questions Positive Work Negative Work No Work Answer Choices The force of friction acts upon a baseball player as he slides into third base. Positive Work Negative Work No Work Work is done because Work and Distance are in parallel directions. Work is Negative because Work and distance are in opposite directions.

Concept Questions Question Answer Choices Kinetic energy is the form of mechanical energy which depends upon the position of an object. If an object is at rest, then it does not have any kinetic energy. If an object is on the ground, then it does not have any kinetic energy. The kinetic energy of an object is dependent upon the weight and the speed of an object. Which of the following statements is the most true about Kinetic Energy?

Concept Questions Question Answer Choices Moving objects cannot have potential energy. Potential energy is the energy stored in an object due to its position. Both gravitational and elastic potential energy are dependent upon the mass of an object. If work is done on an object by a non- conservative force, then the object will either gain or lose potential energy. Which of the following statements is the most true about Potential Energy?

Concept Questions Question Answer Choices Energy, work Power, work Work, energy Work, power Power, energy Force, work Power, force None of these A job is done slowly, and an identical job is done quickly. Both jobs require the same amount of ____, but different amounts of ____. Pick the two words which fill in the blanks in their respective order.

Kinetic Energy

Use g=10m/s2 for the following: (Kinetic Energy) An arrow is drawn back so that 50 Joules of potential energy is stored in the stretched bow and string. When released, the arrow contains ____ Joules of kinetic energy. 50 More than 50 Less than 50 Conservation of Energy: all E transferred from GPE to KE

Rank the Kinetic Energy for the following from least to greatest D<C<B<A C<A<D<B B<C<D<A A<B<C<D

Use g=10m/s2 for the following: A 10-Newton object moves to the left at 1 m/s. Its kinetic energy is approximately ____ Joules. 0.5 1 10 More than 10

Use g=10m/s2 for the following: An object at rest may have __________. speed velocity Acceleration Energy All of the above

Use g=10m/s2 for the following: (Work-Energy Theorem) A 50-kg platform diver hits the water below with a kinetic energy of 5000 Joules. The height (relative to the water) from which the diver dove was approximately ____ meters. 5 10 50 100 GPE=mgh h= GPE/mg

Calculations: A 51.7-kg hiker ascends a 43.2-meter high hill at a constant speed of 1.20 m/s. If it takes 384 s to climb the hill, then determine the kinetic energy change of the hiker. Delta KE = 0J

Calculations: An 878-kg car skids to a stop across a horizontal surface over a distance of 45.2 m. The average force acting upon the car is 7160 N. Determine the initial Kinetic Energy of the car. KE = 324000J

Calculations: (Work Energy) An 878-kg car skids to a stop across a horizontal surface over a distance of 45.2 m. The average force acting upon the car is 7160 N. Determine the work done upon the car. W = 324000J

Potential Energy

Rank the Potential Energy for the following from least to greatest D<C<B<A C<A<D<B B<C<D<A A<B<C<D

Calculations: A 51.7-kg hiker ascends a 43.2-meter high hill at a constant speed of 1.20 m/s. If it takes 384 s to climb the hill, then determine the potential energy change of the hiker. Delta PE = 21888J GPE=mgh

Calculations: (Work Energy) A 51.7-kg hiker ascends a 43.2-meter high hill at a constant speed of 1.20 m/s. If it takes 384 s to climb the hill, then determine the work done upon the hiker W = delta PE = 21888J GPE=mgh

Calculations: (Power) A 51.7-kg hiker ascends a 43.2-meter high hill at a constant speed of 1.20 m/s. If it takes 384 s to climb the hill, then determine the power delivered by the hiker. P = 57 Watts P=W/t = Fd/t = Mad/t

Use g=10m/s2 for the following: A 1200 kg car and a 2400 kg car are lifted to the same height at a constant speed in an auto service station. Lifting the more massive car requires ____ work. Less The same Twice as much Four times as much More than four times as much. W=FD F=ma W=maD

Use g=10m/s2 for the following: A child lifts a box up from the floor. The child then carries the box with constant speed to the other side of the room and puts the box down. How much work does he do on the box while walking across the floor at constant speed? Zero J More than zero J More information needed to determine

Use g=10m/s2 for the following: (Work-Energy Theorem) A platform diver weighs 500 N. She steps off a diving board that is elevated to a height of 10 meters above the water. The diver will possess ___ Joules of kinetic energy when she hits the water. 10 500 510 5000 More than 5000 Net Work= Eneregy W = Fd = KE

Use g=10m/s2 for the following: Lifting the 50 kg crate Lifting the 25 kg crate Both require the same amount of work. Which requires more work: lifting a 50.0 kg crate a vertical distance of 2.0 meters or lifting a 25.0 kg crate a vertical distance of 4.0 meters?

Calculations: Approximate the work required lift a 2.5-kg object to a height of 6.0 meters. 147 J

Calculations: A 65.8-kg skier accelerates down an icy hill from an original height of 521 meters. Use the work-energy theorem to determine the speed at the bottom of the hill if no energy is lost or gained due to friction, air resistance and other non-conservative forces. 101 m/s Net W=KE Fd = .5mv2 V= square Route(KE/.5m)

Calculations: Use the work-energy theorem to determine the force required to stop a 988-kg car moving at a speed of 21.2 m/s if there is a distance of 45.7 m in which to stop it. 4860 N

Calculations: (Work- Energy) A 21.3-kg child positions himself on an inner-tube which is suspended by a 7.28-m long rope attached to a strong tree limb. The child and tube is drawn back until it makes a 17.4-degree angle with the vertical. The child is released and allowed to swing to and from. Assuming negligible friction, determine the child's speed at his lowest point in the trajectory. 2.56 m/s

Calculations: (Work- Energy) A baseball player catches a 163- gram baseball which is moving horizontally at a speed of 39.8 m/s. Determine the force which she must apply to the baseball if her mitt recoils a horizontal distance of 25.1 cm.  514 N

Use g=10m/s2 for the following: (Power) P = W/t Using 1000. J of work, a small object is lifted from the ground floor to the third floor of a tall building in 20.0 seconds. What power was required in this task?

Calculations: Eddy, whose mass is 65.0-kg, climbs up the 1.60-meter high stairs in 1.20 s. Approximate Eddy's power rating. 849 J P = W/t Net W=E E=GPE P=(GPE)/T P=(mgh)t