Force – weight and mass; Hooke’s law; types of force; effect of force (S17/W17)
1. Which row shows the unit for force, the unit for mass and the unit for weight?
2. A piece of scientific equipment is taken on a space ship from Earth to a distant planet.
Which property or properties of the equipment must remain the same on the distant planet?
3. Which conditions are necessary for an object to have weight?
4. A spring obeys Hooke’s law. A load of 10 N hangs from the spring
and causes the spring to extend by 12 mm.
Two springs, identical to the first one, are now joined as shown. A
load of 5.0 N is hung from the springs.
What is the total extension of the combination of the two springs?
A 3.0 mm
B 6.0 mm
C 12 mm
D 24 mm
5. A student stretches a steel spring by hanging a load on it. The
measurements for the extension of the spring are shown in the
table.
What is the value for the spring constant k of the spring?
A 0.50 N / cm B 1.0 N / cm C 2.0 N / cm D 18 N / cm
Hooke’s law:
F= kx
F is force/ load
x is extension
k is spring constant
the greater the load (weight), the longer the extension of the spring, until it reaches the limit of proportionality.
1
6. [0653/41/O/N/17/Q3d] The guitarist investigates the extension of a guitar string made of
steel when different tension forces are used to stretch it.
Fig. 3.3 shows the graph of some results obtained from this experiment.
The guitarist adjusts the note played by a guitar string by adjusting the tension force in the
string. The more the tension force, the higher the note.
The guitarist must only increase the tension force within the limits where Hooke’s Law
applies.
(i) State Hooke’s Law.
...........................................................................................................................................
.......................................................................................................................................[1]
(ii) Use the graph to identify the limit of proportionality for this guitar string.
.......................................................................................................................................[1]
7. [0653/41/M/J/17/Q3] Fig. 3.1 shows a wind surfer on a surf board, driven by the wind, sailing
at a constant speed across the sea. The arrows labelled A, B, C and D show the forces
acting on the surf board.
A – weight
B – thrust
C- upthrust
D - friction
Fig. 3.1
2
(a) (i) State which letter, A, B, C, or D corresponds to
1. frictional force ...................
2. upthrust ................... [1]
(ii) Force A is measured and found to be 1200 N.
State whether force C is 1200 N or has a different value.
Give a reason for your answer.
...........................................................................................................................................
C is 1200 N because the surf board is moving at constant
speed. It is not moving up or down.
......................................................................................................................................
[1]
8. [0653/42/M/J/17/Q3] (a) Fig. 3.1 shows an aircraft flying at a constant height and constant
speed above the Earth’s surface. The arrows labelled A, B, C and D show the forces acting
on the aircraft.
Fig. 3.1
(i) State which letter, A, B, C or D, corresponds to:
1. frictional force, ...................
2. lifting force. ................... [1]
(ii) Force D is measured and found to be 500 000 N.
State whether force B is 500 000 N or has a different value.
Give a reason for your answer.
...........................................................................................................................................
...................................................................................................................................... [1]
(iii) During the flight, the aircraft burns 1000 kg of fuel.
State the effect this has on force D.
Explain why this happens.
effect on force D ................................................................................................................
explanation ........................................................................................................................
...........................................................................................................................................
[1]
3
9. [0653/42/O/N/17/Q3a] Fig. 3.1 shows a helicopter hovering above the ground.
Fig. 3.1
The helicopter stays in one place as it hovers. The turning rotor blades provide the uplift
force to keep it in the air.
On Fig. 3.1 draw two force arrows to show the vertical forces acting on the helicopter.
Label each arrow with the name of the force acting on the helicopter. [3]
10. [0653/43/O/N/17/Q9] Fig. 9.1 shows four forces, P, Q, R and S, acting on a submarine
travelling underwater. The submarine is moving to the right at constant speed.
P – upthrust
Q – friction /
water resistance
R – weight
S – thrust
Fig. 9.1
The submarine has a mass of 3 000 000 kg.
(a) (i) Name force Q. ......................................................................................[1]
(ii) The submarine is travelling at constant speed at a constant depth.
State how the magnitude of force Q compares to the magnitude of force S.
................S and Q has same magnitude. (because the forces are
balanced)...........................[1]
(iii) Calculate the value of force R.
g = 10 N / kg
State the formula you use and show your working.
formula
weight = _mass_ x __gravity__
working
weight = 3 000 000 kg x 10 N/kg = 30 000 000 N
force R = ...................................................... N [2]
4