STAAR REVIEW RC 2: Force & Motion

Front

This illustration shows an example of energy changing forms. Which changes in energy form are illustrated in the diagram?

Back

light - electrical - mechanical and sound

Answer explanation

The correct choice, 'light - electrical - mechanical and sound', accurately reflects the energy transformations shown in the diagram, illustrating how energy can change from one form to another.

Front

At which position does the boulder have the greatest kinetic energy? Options: A, B, C, D

Back

B

Answer explanation

The boulder has the greatest kinetic energy at position B because it is at its lowest point, where potential energy is converted to kinetic energy, maximizing its speed and thus kinetic energy.

Front

Which energy transformation is best shown in this diagram? Options: heat to mechanical, mechanical to light, sound to heat, heat to sound

Back

heat to mechanical

Answer explanation

The diagram illustrates the conversion of heat energy into mechanical energy, which is commonly seen in engines. This transformation is crucial for powering machines, making 'heat to mechanical' the correct choice.

Front

Which graph shows an object slowing down?
Options: A, B, C, D

Back

A

Answer explanation

Graph A shows a decreasing slope, indicating that the object's speed is reducing over time, which means it is slowing down. The other graphs do not depict this behavior.

Front

A person uses a bow to shoot an arrow at a target. In which diagram does the bow and arrow have the greatest amount of potential energy?

Back

B

Answer explanation

The bow and arrow have the greatest potential energy in diagram B, where the bow is fully drawn. This position stores maximum energy due to the tension in the bowstring, ready to be converted into kinetic energy when released.

Front

Which car traveled at an average speed of 20 km/h? Options: A, B, C, D

Back

B

Answer explanation

Car B is the one that traveled at an average speed of 20 km/h, as indicated by the data provided. The other options do not match this speed.

Front

Which object would have the greatest force? Options: a 5 kg object accelerating at 10 m/s², a 5 kg object accelerating at 20 m/s², a 20 kg object accelerating at 4 m/s², a 20 kg object accelerating at 3 m/s²

Back

a 5 kg object accelerating at 20 m/s²

Answer explanation

The force can be calculated using F = m * a. The 5 kg object at 20 m/s² has a force of 100 N, which is greater than the other options: 50 N (5 kg at 10 m/s²), 80 N (20 kg at 4 m/s²), and 60 N (20 kg at 3 m/s²).

Front

An action-reaction pair of forces exists between what in the scenario of an aerialist walking on a tightrope and holding a balancing bar?

Back

the aerialists' feet and the rope

Answer explanation

The correct answer is 'the aerialists' feet and the rope' because the aerialist exerts a downward force on the rope through their feet, while the rope exerts an equal and opposite force upward, illustrating Newton's third law of motion.

Front

The unusual strength of a glue makes it able to hold a heavy object, or load, as shown in the diagram. If the load exerts a strong downward force, the glue

Back

exerts an upward force that is equal to the downward force

Answer explanation

The glue exerts an upward force equal to the downward force of the load, according to Newton's third law. This balance prevents the load from accelerating, allowing it to remain stationary.

Front

If the force of friction resisting the student's push is 4 N, what is the net force acting on the board?

Back

6 N

Answer explanation

The net force is calculated by subtracting the friction force from the applied force. If the student pushes with 10 N and friction is 4 N, the net force is 10 N - 4 N = 6 N, making 6 N the correct answer.