Forces and resultant forceIB MYP Sciences: Subtopic test

1. 1
   A 60 kg astronaut prepares for a mission to the Moon. On Earth the gravitational field strength is 10 N/kg. On the Moon it is 1.6 N/kg.

   (a)

   What is the astronaut's weight on Earth?

   [1 mark]

   • A600 N
   • B60 N
   • C6.0 N
   • D70 N

   (b)

   What happens to the astronaut's mass and weight when she travels to the Moon?

   [1 mark]

   • AHer mass decreases and her weight stays the same
   • BBoth stay the same
   • CBoth decrease
   • DHer mass stays the same and her weight decreases

   (c)

   Calculate the astronaut's weight on the Moon.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A worker in a warehouse in Mumbai pushes a crate along a level floor with a horizontal force of 150 N. The friction force between the crate and the floor is 90 N.

   (a)

   What is the resultant force on the crate?

   [1 mark]

   • A240 N
   • B60 N
   • C150 N
   • D90 N

   (b)

   Which statement describes the motion of the crate?

   [1 mark]

   • AIt moves at a constant speed
   • BIt stays at rest
   • CIt speeds up in the direction of the push
   • DIt slows down

   (c)

   The worker now reduces the push until the crate moves at a constant speed. State the size of the push and explain why.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Mateo, a student in Mexico City, investigates how a spring stretches. He hangs the spring from a stand, adds masses to its lower end one at a time and measures the length of the spring with a metre rule after each mass is added. The spring is 10.0 cm long with no load. Its lengths are 12.0 cm with 100 g, 14.0 cm with 200 g, 16.1 cm with 300 g, 18.0 cm with 400 g and 20.0 cm with 500 g. Take g = 10 N/kg.

   (a)

   State a testable hypothesis for this investigation, and identify the independent variable and the dependent variable.

   [3 marks]

   (b)

   Process the data: calculate the weight of the 300 g mass and the extension it produces, state the relationship between force and extension that the results show, and suggest one way to improve the accuracy of the length readings.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Engineers are designing an electric bus for a city in Morocco. The fully loaded bus has a mass of 12 000 kg. At one moment its motors drive it forward with a force of 9000 N, while friction of 3000 N and air resistance of 2500 N act against its motion. Take g = 10 N/kg.

   (a)

   Discuss the social, economic and environmental implications of friction and air resistance for the design and operation of the bus.

   [6 marks]

   (b)

   Assume the resistive forces stay the same. Calculate the weight of the bus and the resultant force on it. State and explain what happens to the motion of the bus, and state the driving force needed for it to move at a constant speed.

   [6 marks]

   Total for question 4: 12 marks

End of questions