Physics 5054
Multiple Choice
[The questions can be accessed using this link. Consider answering the questions first and then look at the explanations written below.]
A micrometer is used to measure the diameter of a uniform wire.
What is done to obtain an accurate answer?
A Make the micrometer horizontal and then use the scales to find the reading.
B Subtract the fixed-scale reading from the rotating-scale reading.
C Subtract the rotating-scale reading from the fixed-scale reading.
D Use the scales to find the reading and add or subtract any zero error.
Answer: D
The Physics Behind
- Accuracy refers to how close a measurement is to the true or accepted value.
- There are may ways to obtain accurate measurements.
- Reading instruments / measuring at eye level is an example, that is, to deal with parallax errors.
- Another example is reporting the measurement after adding or subtracting any zero error in the instrument.
A car’s acceleration and maximum speed are improved by using an engine of smaller mass and greater driving force.
How many of the underlined quantities are vectors?
A 1 B 2 C 3 D 4
Answer: B
- Vectors are physical quantities that have both magnitude and direction.
- By definition, both acceleration and force, are vector quantities.
The diagram shows part of a ruler that Jin Sol used in her experiment. The ruler is used to find the length of a nail.
What is the length of the nail?
A 2.2 cm B 2.7 cm C 3.2 cm D 3.7 cm
Answer: B
- Length is the distance between two points.
- One point is at 1.0 cm mark and the other is at 3.7 cm mark.
- The length therefore is the difference between these, that is, 2.7 cm.
- The above is also the reason why we always report our measurements after adding/ subtracting zero error. Sometimes our instrument cannot give measurement starting from zero.
Yuna wishes to measure accurately the volume of approximately 40 cm3 of water. She has two measuring cylinders, a larger one that can hold 100 cm3, and a smaller one that can hold 50 cm3. The water forms a meniscus where it touches the glass.
Which cylinder should Yuna use and which water level should he use to ensure an accurate result?
Answer: C
The Physics Behind- The meniscus is the curvature [facing upwards or downwards] that we often see when liquids are placed into a container or volume-measuring tools like graduated cylinder.
- The measurement is taken in consideration of the middle point.
- The above point is the top of meniscus facing downwards or bottom of meniscus facing upwards.
- Apart from correctly reporting the measurement with consideration of meniscus, having a thinner cylinder would give more accurate reading.
- The point mentioned above aligns with the lines calibrated for volume.
- The or graduation or spaces between lines in a graduated cylinder is clearer if it is thinner.
Cassandra travels along the route PQRST in 30 minutes.
What is her average speed?
A 10 km / hour
B 20 km / hour
C 30 km / hour
D 60 km / hour
- Average speed of an object is the total distance it travelled d divided by the total time of trave t.
- Distance d is the total path length travelled by the object.
- In formula form, average speed v is
v = d / t
v = 30 km / 0.5 h
v = 60 km/h
Paths are laid as shown between points X, Y and Z.
Felicia walks along the paths from X to Y to Z and then back to X.
What is the value of the total displacement and of the total distance she travelled?
Answer: B
The Physics Behind- The total distance travelled is the total path length covered covered by the object. Thus, Felicia walked 30 metres.
- The total displacement the straight line distance from a starting point and end point.
- Felicia returned to its original position.
- Therefore, her displacement is zero.
The cyclist, Gargi, takes a ride lasting 250 s.
The graph shows how the distance from the starting position varies with time.
What is Gargi’s average speed for the whole journey?
A 1.0 m/s B 1.2 m/s C 1.5 m/s D 2.0 m/s
Answer: B
The Physics Behind- Average speed is the total distance travelled divided by total time taken.
- A distance of 300 m in 250 s is 1.2 m/s.
Which distance / time graph represents the motion of an object moving at constant speed?
Answer: D
The Physics Behind- In a distance-time graph, the speed of an object is represented by the gradient.
- A constant gradient is given by a straight line and is therefore is a constant speed.
- There are 2 straight lines among the options.
- Zero speed in option C which is a constant i.e. remains zero.
- A non-zero speed in option D which is also a constant.
- However, the question states that the object is moving at constant speed. So the answer is D.
The graph shows how the speed of a car changes with time.
Which calculation gives the distance travelled by the car in 24 seconds?
Answer: C
The Physics Behind- In a distance-time graph, area under the graph represents the distance covered by an object.
- The figure under the graph is a triangle. The answer therefore is C, following the formula of an area of triangle.
The table shows how the speeds of four bodies, A, B, C and D, change with time.
Which body has an acceleration that is not constant?
Answer: A
The Physics Behind- Acceleration is defined as the rate of change in velocity.
- A constant acceleration therefore is happening when the change in velocity is the same at equal interval of time.
- The answer is A.
The graph shows how the speed of a car changes with time.
Between which two times is the car stationary?
A U and V B V and W C W and X D X and Y
Answer: D
- An stationary car means a car with zero velocity / speed.
- Between time X and Y, the car's speed is zero.
Which speed-time graph represents the motion of a railway train making a short stop at a station?
Answer: C
The Physics Behind- A train making a short stop, when shown in a speed-time graph should have
- decreases magnitude at first,
- zero magnitude in a short time, and
- increases magnitude after.
- Option C gives these magnitudes in order.
Grant hits a ball over the net.
In which position is the ball accelerating?
A P and Q only
B P and R only
C Q and R only
D P, Q and R
Answer: D
The Physics Behind- Acceleration is caused by a resultant force F.
- At points P, Q, and R, gravity is the resultant force acting on the object.
- At these points, therefore, the object is accelerating.
An engine pulls a truck at constant speed on a level track.
The link between the engine and the truck breaks. The driving force on the engine remains constant.
What effect does this have on the engine and on the truck?
Answer: B The Physics Behind
- When the engine pulls the truck along the straight track:
- The resultant force is zero. This is because a zero resultant force gives zero acceleration.
- The acceleration is zero because the speed along a straight line is constant.
- The zero resultant force is due to the engine's force and friction having an equal magnitude but opposite in direction.
- When the link breaks,
- the engine
- will experience lesser friction so there is now a resultant force,
- as the object now has lesser mass which affects acceleration too [Newton's 2nd Law]
- therefore speeds up.
- the truck
- will no longer experience the engine's force
- only friction acts on the truck, opposing its motion
- therefore slows down.
On which car is there a resultant force?
A a car moving along a straight horizontal road at constant speed
B a car moving around a bend at constant speed
C a car moving uphill at constant velocity
D a car that is stationary
Answer: B
The Physics Behind
- Resultant force causes acceleration.
- Acceleration is change in velocity over time.
- Options A, C and D are all showing no change in velocity and therefore have no acceleration and resultant force.
- On the other hand, option B constantly changing its velocity.
- Velocity is a vector.
- The magnitude [speed] of velocity is constant.
- But the direction always changes when moving along a curvature.
Which diagram shows the addition of the 4.0 N and the 3.0 N forces?
Answer: A
The Physics Behind- One way to determine the sum of vectors graphically is by
- representing them, using a scale, by arrows,
- connecting arrows tip-to-tail, and
- measuring the straight line distance between the tail of the first arrow and the tip of the last.
- The above is done in option A.
Forces of 4.0 N and 2.0 N act at a point.
Which scale diagram shows the forces that have a resultant of 4.0 N?
Answer: B
The Physics Behind- Another method to determine the resultant vector e.g. resultant force is the use of parallelogram method.
- In parallelogram method,
- tails of arrows representing vectors are drawn from the same point, say point X.
- arrows drawn are used to complete a parallelogram.
- the diagonal with one endpoint at the initial point X is the resultant.
The minimum braking distance for a car is tested on a dry road. The test is then repeated on a wet road.
What happens to the braking distance and to the frictional force between the tyres and the road?
Answer: C
The Physics Behind- Braking requires friction. The greater the friction, the shorter the breaking distance.
- On a wet road, the friction is less since water is a lubricant. The breaking distance therefore is longer.
Madelyn drives her car along a level road.
The diagram shows all of the horizontal forces acting on her car.
Which statement is correct?
A The car is slowing down.
B The car is speeding up.
C The car is moving at a constant speed.
D The car is moving backwards.
Answer: B
The Physics Behind
- The resultant force is directed to the right.
- The car therefore will have an acceleration to the right.
- Since the car originally moving to the right, acceleration to the right means its magnitude of velocity [speed] increases.
Cleo measures a stack of razors as part of her Physics experiment.
The figure at the left shows the zero error of a Vernier Caliper and the diagram at the right shows the device’s scales while measuring a stack of 10 razors.
What is the correct reading in the caliper?
A 3.00 cm
B 1.06 cm
C 1.03 cm
D 0.30 cm
Answer: C
The Physics Behind
- The Vernier caliper [see diagram at the right] gives
- 1.0 cm in the main scale, and
- 0.06 cm in the Vernier scale.
- Cleo could have just give the measurement as 1.06 cm but...
- there is a zero error as given at the diagram at the right, and
- the zero error is
- 0.0 cm + 0.03 cm
- 0.03 cm
- the zero error here means that Cleo started the measurement from a mark after the 0 mark and that must be deducted from the 1.06 cm. The answer should be 1.06 cm - 0.03 cm [or 1.03 cm].
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