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DP IB Physics: SL

Topic Questions

Home / IB / Physics: SL / DP / Topic Questions / 2. Mechanics / 2.3 Work, Energy & Power / Structured Questions


2.3 Work, Energy & Power

Question 1a

Marks: 4

A toy company are investigating the workings behind several types of toys. 

(a)
Select, by placing a tick () in the correct box, the main form of energy used by each toy.

Toy

Kinetic Energy

Gravitational Potential Energy

Elastic Potential Energy

A catapult

 

 

 

An action figure falling using a parachute

 

 

 

A wind-up bouncing rabbit

 

 

 

A train moving along a train track

 

 

 

[4]
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    Question 1b

    Marks: 2

    The catapult from part (a) is undergoing testing. The spring constant of the elastic band in the catapult is 92 N m−1. In one test the band is extended by 0.3 m. 

    (b)
    Calculate the elastic potential energy stored in the elastic band of the catapult.
    [2]
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      Question 1c

      Marks: 3

      An action figure from part (a) of mass 250 g is dropped from a height of 5 m. 

      (c)
      Calculate the gravitational potential energy of the action figure in this experiment. 
      [3]
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        Question 1d

        Marks: 2

        A new type of pushchair for dolls is being developed. In one round of testing a pushchair has a force of 20 N applied for a distance of 5 m at an angle of 45° to the horizontal. 

        (d)
        Calculate the work done on the pushchair. 
        [2]
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          Key Concepts
          Work Done

          Question 2a

          Marks: 2

          At an athletics training camp, runners are being tested for their speed, efficiency and power. A runner with a mass of 52 kg manages to maintain a constant velocity of 7 m s−1

          (a)
          Calculate the kinetic energy of the runner. 
          [2]
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            Key Concepts
            Kinetic Energy

            Question 2b

            Marks: 3

            The runner from part (a) runs for 12 seconds.

            (b)
            Calculate her power. 
            [3]
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              Key Concepts
              Power

              Question 2c

              Marks: 3

              At the training camp runners are kept on a strict diet to maximise performance. 

              (c)
              Identify the following types of energy: 

              (i)
              The energy stored in the athlete's muscles.
              [1]

              (ii)
              Two forms of wasted energy transfer produced from the stored energy above.
              [2]
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                Question 2d

                Marks: 2

                Runners are also analysed for their efficiency. The same runner from parts (a) and (b) eats an energy bar that provides 800 000 J of energy. 

                (d)
                Calculate the efficiency of her run assuming that all the energy from the bar is transferred to her body for use on the run. 
                [2]
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                  Key Concepts
                  Efficiency

                  Question 3a

                  Marks: 4

                  The rising price of petrol is inspiring car companies to produce more efficient electric models. 

                  (a)
                  Identify by placing a tick () in the correct boxes the useful and wasted energy transferred from the chemical reaction happening inside a petrol car. 

                  Energy type

                  Useful

                  Wasted

                  Sound

                   

                   

                  Thermal

                   

                   

                  Electrical

                   

                   

                  Kinetic

                   

                   

                  [4]

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                    Key Concepts
                    Efficiency

                    Question 3b

                    Marks: 9

                    Some energy within a system is stored and some is transferred. 

                    (b)
                    Place a tick () in the correct box to identify whether the following energy types are stores or transfers. 

                    Energy type

                    Transfer

                    Store

                    Chemical  

                     

                    Nuclear  

                     

                    Sound  

                     

                    Light  

                     

                    Kinetic  

                     

                    Internal  

                     

                    Elastic  

                     

                    Gravitational potential  

                     

                    Electrical  

                     

                    [9]
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                      Question 3c

                      Marks: 2

                      Driving safety organisations are worried that electric cars are more powerful than petrol or diesel cars causing them to be very dangerous.

                      In a test drive, the thrust from an electric car engine is 200 N when the car maintains a constant speed of 27 m s−1.

                      (c)
                      Calculate the power of the car. 
                      [2]
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                        Key Concepts
                        Power

                        Question 3d

                        Marks: 3
                        (d)
                        State:
                         
                        (i)
                        Whether electric or petrol cars have more wasted energy.
                        [1]
                        (ii)
                        Two types of wasted energy in a car energy system.
                        [2]
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                          Key Concepts
                          Efficiency

                          Question 4a

                          Marks: 2

                          Astronauts are in training for a planned mission to land on the surface of Jupiter. 

                          (a)
                          Identify, by placing a tick () in the box(es), which of the following tasks will be more difficult to carry out due to the larger acceleration of free fall on Jupiter. 

                          Task

                          More difficult

                          Throwing a ball up from the surface  
                          Driving a car along the surface  
                          Stretching a spring whilst setting up a tent  
                          Launching a rocket from the surface  
                          [2]
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                            Question 4b

                            Marks: 3

                            A ball is dropped from a height of 2 m towards the surface of Jupiter. The acceleration of free fall on Jupiter is 24.58 m s−2

                            (b)
                            Calculate the speed of the ball just as it hits the surface. Assume that no energy is lost to the surroundings.

                            (i)
                            State the relationship, in symbols, between gravitational potential energy at the point the ball is dropped from and the kinetic energy just before it hits the surface
                            [1]
                            (ii)
                            Rearrange the relationship found in part (i) to obtain an equation for v, the speed of the ball when it hits the surface
                            [1]
                            (iii)
                            Hence, calculate v
                            [1]
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                              Question 4c

                              Marks: 5

                              The mass of the rocket upon its launch from Jupiter is 18 × 10kg. It takes 300 seconds to travel the 3000 km to the edge of Jupiter's atmosphere. 

                              (c)
                              Calculate:
                               
                              (i)
                              The weight of the rocket.
                              [2]
                              (ii)
                              The minimum power required by the rocket to leave the surface of Jupiter. 
                              [3]
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                                Key Concepts
                                Power

                                Question 4d

                                Marks: 3

                                Astronauts have developed special tents with stiff springs to erect on the surface of Jupiter. The springs hang freely vertically with one end fixed to the tent and the other with a mass secured.

                                (d)
                                Label the diagram below to show the spring when the gravitational potential energy (ΔEp), kinetic energy (Ek) and elastic potential energy (Ep) are each at their maximum. 
                                2-3-q4d-sl-sq-easy-phy
                                [3]
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                                  Question 5a

                                  Marks: 3

                                  A violin maker is conducting materials testing on various new strings. The first string has a spring constant of 23 000 N m−1 and is extended by 0.06 m before it breaks.

                                  (a)
                                  Calculate the force applied to the string just before it breaks. 
                                  [3]
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                                    Question 5b

                                    Marks: 4

                                    The string has a mass of 1.97 × 10−4 kg. When the string breaks, assume all elastic potential energy is transferred to kinetic energy. 

                                    (b)
                                    Calculate the speed of the string upon breaking. 
                                    [4]
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                                      Question 5c

                                      Marks: 2

                                      The force-extension graph of a different string is shown below. 

                                      (c)
                                      Identify the elastic limit and breaking point by labelling the graph. 
                                      2-3-5c-q-sl-sq-easy-phy
                                      [2]
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                                        Question 5d

                                        Marks: 3
                                        (d)
                                        Calculate the work done on the string up to the elastic limit. 
                                        2-3-5d-q-sl-sq-easy-phy
                                        [3]
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                                          Key Concepts
                                          Work Done