Multiple choice AS 2019.w13

Which quantity with its unit is correct?

• acceleration of a bicycle = 1.4 m/s

• electric current in a lamp = 0.25A/s

• electric potential difference across a battery = 8.0 J/C

• kinetic energy of a car = 4500 N/m

Which two units are not equivalent to each other?

• N m and kgm^2 s^–2

• Ns and kgm s^–1

• J s^–1 and kgm^2 s^–3

• Pa and kg m s^–2

The arrow represents a vector R. Which diagram does not represent R as two perpendicular components?

• 
• 
• 
• 

What could reduce systematic errors?

• averaging a large number of measurements

• careful calibration of measuring instruments

• reducing the sample size

• repeating measurements

The power loss P in a resistor is calculated using the formula  $p=\frac{V^2}{R}$  The percentage uncertainty in the potential difference V is 3% and the percentage uncertainty in the resistance R is 2%. What is the percentage uncertainty in P?

• 4%

• 7%

• 8%

• 11%  

A lead sphere is released from rest at point X, a long way above the surface of a planet. The sphere falls in a vacuum. After a time of 4.0 s, it has fallen through a vertical distance of 3.0 m. Assume the acceleration of free fall is constant. How far will the sphere have fallen from point X at a time of 20 s after its release?

• 15 m

• 75 m

• 80 m

• 2000 m

A box rests on the Earth, as shown. Newton’s third law describes how forces of the same type act in pairs. One of the forces of a pair is the weight W of the box. Which arrow represents the other force of this pair?

• A

• B

• C

• D

A snowflake is falling from the sky on a still day. Its weight acts vertically downwards and air resistance acts vertically upwards. As the snowflake falls, air resistance increases until it is equal to the weight and there is no resultant force acting on the snowflake. When the forces become equal, which statement is correct?

• The snowflake accelerates.

• The snowflake decelerates.

• The snowflake is stationary.

• The snowflake moves at a constant velocity.

Two objects X and Y in an isolated system undergo a perfectly elastic collision. The velocities of the objects before and after the collision are shown. What is the speed v of Y after the collision?

• 2.0 m s^–1

• 18 m s^–1

• 22 m s^–1

• 24 m s^–1

A solid sphere, which is less dense than water, is held completely immersed in water a few metres below the surface. The density of the water is uniform. The sphere is released. Immediately after release, the sphere rises. Which row correctly describes the changes in the upthrust on the sphere and the resultant force on the sphere?

• upthrust on the sphere is constant so resultant force on the sphere is increasing

• upthrust on the sphere is constant so resultant force on the sphere is decreasing

• upthrust on the sphere is decreasing so resultant force on the sphere is increasing

• upthrust on the sphere is decreasing so resultant force on the sphere is decreasing