UCL CENTRE FOR LANGUAGES
& INTERNATIONAL EDUCATION (CLIE)

UPC Practice Entry Tests

Test: Physics 1

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1.	The following are five properties of an object. Which one of the properties is a vector quantity?

	mass
	volume
	weight
	density
	surface area
Incorrect. Remember that a vector is a mathematical object that has direction in space.

2.	The following are five properties of an object. Which one of the properties would change if the body were taken to the moon, keeping its temperature constant?

	mass
	volume
	weight
	density
	surface area
Incorrect. Remember that the acceleration due to gravity is smaller on the Moon than it is on Earth.

3.	Which one of the properties can be expressed in Ns²m^-4?

	mass
	volume
	weight
	density
	surface area
Incorrect. You can use Newton's second law to convert one newton in base units.

4.	A metal cube, with each side 2 cm in length, has a density of 8 g/cm³. What is the mass of the cube?

	2g
	4g
	8g
	16g
	64g
Incorrect. Note that density is mass per unit volume.

5.	A boy of mass 40 kg balances evenly on two stilts, each having an area of 8 cm² in contact with the ground. What is the pressure exerted by one stilt?

	50 N/cm²
	40 N/cm²
	25 N/cm²
	5 N/cm²
	2.5 N/cm²
Incorrect. Pressure is force per unit area.

6.	A ship is sailing slowly due east, and a passenger is on the deck at P. In the diagram the points A, B, C, D and E are marked on the deck. Towards which of these points should the passenger walk at a suitable speed in order to move due north?

	A
	B
	C
	D
	E
Incorrect. You may need to clarify your understanding of the concept of relative velocity.

7.	A car's tyres are inflated so that an area of 50 cm² of each tyre is in contact with the ground. If the mass of the car is 1600 kg and it is evenly distributed between the four tyres, what is the pressure the road exerts on each tyre?

	8 N/cm²
	32 N/cm²
	80 N/cm²
	160 N/cm²
	320 N/cm²
Incorrect. First calculate the force due to gravity on each tyre.

8.	An electric heater is rated 250 V, 1000 W. If electricity costs 7p per kWh what is the cost of running the heater for 5 hours?

	3.5p
	7p
	17.5p
	35p
	70p
Incorrect. It costs 7p to run a 1000 W appliance for one hour.

9.

Similar cells, ammeters and resistors are used in the circuit shown.

The cells and ammeters have negligible resistance. When one cell is connected in series with one ammeter and one resistor the ammeter reading is 0.1 A.

What is the value of the current through ammeter A₁ in the circuit shown in the diagram?

	0.1 A
	0.2 A
	0.3 A
	0.4 A
	0.5 A
Incorrect. The potential difference across a resistor of resistance R through which a current I passes equals RI.

10.	In the circuit of Question 9, what is the value of the current through ammeter A₂?

	0.1 A
	0.2 A
	0.3 A
	0.4 A
	0.5 A
Incorrect. You will need to use Kirchhoff's laws.

11.	A body accelerates from rest at 4 m/s² for 5s. What is its average speed during these 5 seconds?

	0.8 m/s
	1.2 m/s
	9 m/s
	10 m/s
	11 m/s
Incorrect. First, calculate the final speed after 5s. Then calculate the average speed.

12.	Two springs (of spring constant k = 1.0 Ncm^-1) are suspended vertically and in parallel (next to each other). If a load of 200 g is attached to their common end so that each spring stretches by the same amount, what is the stretch equal to ? (g = 10 m/s²).

	0.5 cm
	1 cm
	2 cm
	4 cm
	8 cm
Incorrect. What is the spring constant of two identical springs in parallel?

13.	The graph shows the temperature change that takes place when a pure substance is cooled. What change of state does the section x-y of the graph represent?

	a solid to a gas
	a liquid to a solid
	a solid to a liquid
	a gas to a liquid
	a liquid to a gas
Incorrect. Note that the transformation occurs at constant temperature.

14.	What is a particle with a mass of approximately 1 atomic mass unit and a charge of +1 called?

	an electron
	a gamma particle
	a positron
	a proton
	an alpha particle
Incorrect. A positron and a proton both have a charge of +1. Which one has a mass of one atomic mass unit?

15.	The sketch shows the masses and positions of two moons relative to planet X. The gravitational force between 4m and X is F₁. The gravitational force between m and X is F₂. Which one is the correct relationship between the two forces?

	F₁ = F₂
	F₁ = 2F₂
	F₂ = 2F₁
	F₂ = 4F₁
	F₁ = 4F₂
Incorrect. The gravitational interaction between two masses is proportional to the product of the two masses and inversely proportional to the square of the distance between them.

16.	In the qualifying lap for a motor racing Grand Prix, one driver completes the 1.8 km circuit in 40 seconds. Her average speed for the lap is:

	0.0045 ms^-1
	22 ms^-1
	40 ms^-1
	45 ms^-1
	72 ms^-1
Incorrect. the average speed is total distance travelled over total time taken to travel it.

17.	Which ONE of the following statements about speed and velocity is FALSE?

	Speed and velocity are both measured in ms^-1.
	Velocities must indicate a direction.
	Speeds and velocities never have the same size.
	Velocity indicates both the speed and the direction that an object travels away from a reference point.
	Objects can travel at different speeds to achieve the same average velocity.
Incorrect. Speed is a scalar quantity (i.e. magnitude with no direction), whereas velocity is a vector quantity (i.e. both magnitude and direction).

18.	The velocity versus time graph below represents the motion of an object being acted on by a constant force. Which option shows the correct values for the instantaneous speed after 3 seconds and the average speed over the first 3 seconds of the motion?

	A
	B
	C
	D
	E
Incorrect. The acceleration is constant (i.e. the gradient of the graph) so the average speed is initial speed plus final speed divided by 2. The instantaneous is the speed on the y-axis at t = 3 s (i.e. 12 m/s).

19.	A motorcycle of mass 250 kg accelerates from rest to a speed of 30 ms^-1 in 6 seconds. The total forces opposing this motion equal 1500 N. The thrust produced by the car's engine is:

	250 N
	1250 N
	1500 N
	2750 N
	3000 N
Incorrect. You may want to revise Newton’s second law of motion that says the sum of all external forces is proportional to the mass’s acceleration.

20.

Two trolleys of mass 1 kg and 0.8 kg, travelling towards each other on a linear air track collide head on. The 1 kg vehicle is initially travelling at 2 ms^-1 towards the 0.8 kg vehicle which is travelling at 3 ms^-1.

If after the collision, the 1 kg vehicle returns along its original path at 0.5 ms^-1, the 0.8 kg vehicle will have a velocity of:

	0.125 ms^-1to the left
	0.125 ms^-1 to the right
	0.5 ms^-1 to the left
	0.5 ms^-1 to the right
	5.375 ms^-1 to the right
Incorrect. Think of the conservation of momentum.

21.	A 12 V car battery supplies a steady current of 200 A for 2.5 ms. The energy supplied by the battery is:

	3 J
	6 J
	62 J
	300 J
	6 kJ
Incorrect. Recall that the electrical energy is proportional to, both voltage and current, as well as time

22.	A constant current of 50 μA is used to charge a capacitor for 3 minutes. The potential difference across the capacitor at the end of this time is 6 V. The capacitance of the capacitor is:

	25 μF
	47 μF
	100 μF
	555 μF
	1500 μF
Incorrect. Apply the definitions of capacitance and electric current.

23.	Circular waves spreading out in a ripple tank travel a distance of 20 cm in 2.5 seconds. The speed of the waves is:

	0.05 ms^-1
	0.08 ms^-1
	8.0 ms^-1
	12.5 ms^-1
	50 ms^-1
Incorrect. The speed of a wave is proportional to the wavelength and inversely proportional to the period of a wave.

24.	A ray of monochromatic light emerging from a parallel-sided block of glass in to air, strikes the top side at angles shown in the diagram. The refractive index of the material of the parallel-sided block for this light ray is:

	0.54
	0.68
	1.53
	1.71
	1.86
Incorrect. Remind yourself of Snell’s law of refraction.

25.	Photons of light resulting from the transition labelled B have a frequency: (You may assume Planck's constant h = 6.63 x 10^-34Js)

	equal to 8.17 x 10^-14Hz
	lower than those resulting from transitions A and C
	equal to 6.12 x 10¹⁴ Hz
	higher than that from transition C, but lower than that for transition A
	equal to 5.42 x 10^-19 Hz
Incorrect. The difference of atomic energy levels is proportional to the frequency of light that is absorbed or emitted.

26.

The gravitational potential difference between a point at the surface of a certain planet and a point 10 m above that surface is 4.0 J kg^-1. Assuming the gravitational field is uniform, the work done, expressed in joules, in moving a mass of 2.0 kg from the surface to a point 5.0 m above the surface is:

	0.16
	1.0
	2.0
	4.0
	16
Incorrect. Recall the relation between gravitational potential and gravitational potential energy and consider that the field is uniform.

27.	Two long parallel wires X and Y carry currents of 3 A and 5 A, respectively. The force experienced per unit length by X is 5x10^-5 N to the right as shown in the diagram. The force per unit length experienced by wire Y is:

	2x10^-5N to the left.
	3x10^-5N to the right.
	3x10^-5N to the left.
	5x10^-5N to the right.
	5x10^-5N to the left.
Incorrect. Use the formula for the magnetic force between to current carrying conductors and the left hand rule for the direction of the force.

28.

Monochromatic light of wavelength 600 nm is used in a spectrometer to illuminate a diffraction grating set normally to the collimator. The grating has
3x10⁵ lines per metre. The telescope is used to scan the field to one side of the straight-through position. Not counting the 'straight-through' image, the maximum number of diffracted images of the slit visible to the observer will be:

	2
	5
	8
	10
	11
Incorrect. The law of diffraction says that d sin(theta)=n(wavelength).

29.

A uniform wire, fixed at its upper end, hangs vertically and supports a weight at its lower end. If its radius is r, its length L and the Young's modulus for the material of the wire is E, the extension is:
1 directly proportional to E.
2 inversely proportional to r.
3 directly proportional to L.

Which statements are correct?

	1, 2, 3
	1, 2
	2, 3
	1 only
	3 only
Incorrect. You should recall that Young modulus is stress divided by strain, and recall how stress and strain are relating to force, area, extension and natural length.

30.	An ideal gas is heated at constant volume until its pressure doubles. Which one of the following statements is correct?

	The mean speed of the molecules doubles.
	The number of molecules doubles.
	The mean square speed of the molecules doubles.
	The number of molecules per unit volume doubles.
	The root mean square speed of the molecules doubles.
Incorrect. Revise the ideal gas equation and the relations of the rms speed and average speeds of molecules in an ideal gas.