## IB Physics SL Paper 1 Question Bank

**1.) What is a unit of force?**

A.) m/Js

A.) J m

A.) J/m

A.) J/ms

**Answer: C**

The metric unit of force is the joule per meter (J/m). In the field of mechanics, a joule is defined as the amount of work required to move an item one meter across a distance of one newton in the direction of application (1 J = 1 Nm). Newton is therefore equal to one joule per meter.

**2.) The length of the side of a cube is 3.0 cm Â± 5%. The mass of the cube is 27.0 g Â± 7%. What is the percentage uncertainty of the density of the cube?**

A.) 22

A.)Â 12

A.)Â 8

A.)Â 14

**Answer: A**

Volume of the cube is 3 x 3 x 3, therefore the uncertainties will also get added 3 times** (not multiplied)**. Therefore 5 x 3 = **Â± 15%** Even though density = mass / volume, the percentage uncertainties get added, therefore, the percentage for the density is 15 + 7 = **Â± 22%**

**3.) A truck has an initial speed of 25 ms ^{-1}. It decelerates at 5.0 ms^{-2}. What is the distance taken by the truck to stop?**

A.)Â 12.5 m

A.)Â 5 m

A.)Â 125 m

A.)Â 62.5 m

**Answer: D**

To find the distance, the time needs to be calculated. Therefore, using an equation of motion, v = u + at and substituting the values that we have, we have

0 = 25 + (-5)t

v is the final speed which is 0 since the question says that the truck comes to a stop. The deceleration is 5 so the value of the acceleration would be -5. Therefore, calculating t, we have 5t = 20 â†’ t = 4 s.

Using the time, the distance can be found using another equation of motion: s = ut + Â½ at^{2} where s is the distance. Therefore, substituting the values that we have,

s = (25)(5) + Â½ (-5)(5)^{2}

S = 125 + (-62.5) = **62.5 m**

**4.) A heat engine does 250 J of work during one cycle. In this cycle, 750 J of energy is wasted. What is the efficiency of the engine in percentage?**

A.)Â 25%

A.)Â 33.3%

A.)Â 50%

A.)Â 75%

**Answer: A**

Total energy is 250 + 750 = 1000 J

Efficiency of the engine = (Work done/Total energy)*100

= (250/1000)*100 = **25%**

**5.) A driving force F acts on a car which moves with a constant velocity v. The quantity Fv is equivalent to:**

A.)Â Useful power released by the engine of the car

A.)Â Work done by the car

A.)Â Energy produced by the car

A.)Â Rate of change of momentum of the car

**Answer: A**

The quantity Fv is a result of multiplying the driving force and the velocity (Force x Velocity). The output you get by multiplying these quantities is Power. **Power = Force x Velocity**

**6.) There is water boiling in a pot. The boiling water molecules leave to form vapor. The temperature of the water and the vapor are the same. How do the average kinetic and potential energy of the molecules change when the liquid water boils to form vapor?**

A.)Â No change in average potential energy & no change in average kinetic energy

A.)Â No change in average potential energy & increase in average kinetic energy

A.)Â Increase in average potential energy & no change in average kinetic energy

A.)Â Increase in average potential energy & increase in average kinetic energy

**Answer: C**

When there is a phase change, the temperature stays constant therefore implying that the average kinetic energy also remains unchanged. During the vaporization stage, there is a certain amount of energy that the molecule attains thereby increasing the internal energy of said molecules. This means that the average potential energy increases.

**7.) A sound wave travels from hot air to cold air. How does the frequency and the wavelength of the wave change?**

A.)Â Frequency remains unchanged & wavelength increases

A.)Â Frequency remains unchanged & wavelength decreases

A.)Â Frequency increases & wavelength increases

A.)Â Frequency decreases & wavelength decreases

**Answer: B**

Wave velocity = frequency x wavelength

Therefore, when the temperature decreases, velocity decreases thereby decreasing the wavelength of the wave. The frequency of the wave is not affected by the temperature of the air so it remains unchanged.

**8.) A mass is moving along a horizontal circle with constant speed. Which of the following options are correct about the magnitude and direction of the mass?**

A.)Â Magnitude is constant and direction is constant

A.)Â Magnitude is constant and direction is changing

A.)Â Magnitude is changing and direction is constant

A.)Â Magnitude is changing and direction is changing

**Answer: B**

Since the speed is a scalar quantity and only represents the magnitude, the magnitude will remain constant as the mass moves along the horizontal circle. However, the velocity changes since there is a change in the direction at every point when the circle moves across the horizontal circle.

**9.) The average binding energy per nucleon for Carbon 12 is 7.68 MeV. What is the total energy required to separate the nucleons of one nucleus of Carbon 12?**

A.)Â 92 MeV

A.)Â 46 MeV

A.)Â 138 MeV

A.)Â 174 MeV

Answer: A

Binding energy per nucleon = Binding energy (B) / Number of nucleons (A)

Since we need to find the binding energy, the equation can be rearranged

Binding energy (B) = Binding energy per nucleon x Number of nucleons

Number of nucleons is 12 and binding energy per nucleon is 7.68, so:**Binding energy (B) = 12 x 7.68 = 92.16 MeV approximately, 92 MeV**

**10.) A horizontal string has one end fixed to a wall. As seen, a transverse pulse travels along the string.**

**Which of the following claims about the reflected pulse in relation to the forward pulse is true?**

I) The pulse is inverted

II) It has less energy

III) The pulse moves more slowly

A.)Â I and II

A.)Â I and III

A.)Â I, II and III

A.)Â II and III

**Answer: D**

When the wave hits the wall, some of the energy is transferred to the wall. Therefore, after some of the energy passes on and when the wave is reflected, the pulse is reflected with lesser energy. Furthermore, when the pulse has lesser energy, it is also bound to move with a lower velocity due to its lesser energy.