Multiple Choice: Forces, Dynamics and Mechanics

Q11. Use a distance-time graph for a journey to school to calculate the average speed for the journey.

Average speed = total distance travelled/total time taken

Average speed = 800/160 = 5 m/s

Q12. Which of the following is Newton's Third Law?

A	For every action there is an equal and opposite reaction.
B	What goes up must come down.
C	The acceleration that a resultant force produces depends on the size of the force and mass of the object.
D	An object will continue to stay at rest or move with uniform speed unless a force acts on it.

Q13. On Mars the gravitational field strength is 4.0 N/kg.

How much would a 60 kg person weigh on Mars?

weight = mass x gfs

weight = 60 x 4.0 = 240 N

Q14. A student sets up two cogs.

Cog A has 10 teeth and cog B has 20 teeth.

Cog A is turned two times.

How many times does cog B turn?

Q15. A car travels at 72 km/h.

How fast is this in metres per second (m/s)?

72 km = 72,000 m

1 h = 60 x 60 s = 3,600 s

speed = distance travelled/time taken

speed = 72000/3600 = 20 m/s

Q16. Which one of the following uses of forces causes a rotation?

A	Lowering a book vertically from a shelf
B	Opening a door
C	Lifting a book vertically onto a shelf
D	Sitting in the centre of a see-saw

Q17. A skydiver falls from a plane.

What is the name of the downward force in the diagram?

Q18. A cyclist travels 750 m in 50 seconds.

Calculate the speed of the cyclist.

speed = distance travelled/time taken

speed = 750/50

speed = 15 m/s

Q19. On the Moon the gravitational field strength is 1.6 N/kg.

Calculate the weight of a 80 kg astronaut on the moon.

weight = mass x gfs

weight = 80 x 1.6

weight = 128 N

Q20. Look at the distance-time sketch graph below.

Which line shows the largest average speed?