Past Paper Qs (CORE PHYSICS 1, Booklet 2)

Question 1

Einstein imagined a person in a large box without any windows he suggested that, with no way to see outside, the person could not tell whether they were:

. Experiencing gravity on earth
. In deep space far away from any effects of gravity but being accelerated at a rate of 9.81m/s

Account for Einstein’s suggestion by explaining in each case what a person in the box would feel through their feet. It may help to assume the person has mass m. (6)

Answer 1

Earth:
- downwards force of weight acting on person
- upward reaction force acting on person
- therefore no resultant force (person isn’t accelerating through the floor)
- therefore normal contact (reaction) force acting on person= weight (mg)

Space:
- must be a resultant force as box is accelerating
- force exerted by floor onto foot is = ma (a=g, 9.81)

Comparison:
- in both cases person feels same force, of mg, from the floor

Question 2

An exhibit in a science museum requires the observer to use a pump to create air bubbles in a column of liquid. The bubbles then rise.

*(ii) it is observed that the larger bubbles reach the top of column of liquid in a shorter time than the smaller bubbles.
By considering the forces acting on a bubble as it rises, explain this observation. (3)

Answer 2

. Both bubbles experience up thrust and drag
. As upthrust increases drag increases, however upthrust increases more than drag
. Upthrust= weight of fluid displaced, since volume of larger bubble is greater it displaces more water
Hence experiences greater upthrust
. Larger bubble therefore experiences a greater resultant force in comparison the the smaller bubble

Question 3

State what is meant by drift velocity when applied to a metal conductor (1)

Answer 3

. Overall net mean of charge carriers in the lattice

Question 4

Two conductors of the same material and length carry the same current. Conductor x has twice the cross-sectional area of conductor y.

*(ii) explain the difference in resistance of conductor x and conductor y in terms of the difference in drift velocity. (3)

Answer 4

. Resistance of y is greater than resistance of x
. V is greater for y
- therefore electrons gain more kinetic energy between collisions with lattice ions, as collisions are more frequent
. Therefore greater p.d required for given current

Question 5

Explain, in terms of energy, the difference between potential difference (p.d)
And electromotive force (EMF). (2)

Answer 5

-P.d is there electrical energy transferred between two points
- EMF is the energy supplied to the circuit

Question 6

Explain why, when a slinky is hanging from a persons hand, the coils are extended more at the top then at the bottom. (2)

Answer 6

• coils at the top support the coils below, so a greater force acts on the top coils
• coils at the top have to support the weight of the coils below as well

Question 7

A ball is dropped from the same height, and at the same time, as the top of the slinky is released

*(1) by considering the forces acting on the top coils of the slinky, explain why it fell after than the ball. (3)

Answer 7

. Ball is acted on by its weight alone
. Top coils acted on by weight but also elastic tension due to extension of coils
- therefore acceleration is greater (greater resultant force)

Question 8

When slinky is released suggest why the bottom coils remain in the same position in the three photographs. (1)

Answer 8

• they are being acted on by weight downwards and elastic tension upwards, forces on them remain balanced

Question 9

*A student is asked to explain which of two filament lamps will be brighter when they are connected in parallel across a power supply. She is told that the resistance of lamp A is greater than the resistance of lamp B.
The student wrote the following explanation that contains some mistakes:
”The current is the same in both lamps. Because lamp A has a higher resistance, it is harder for the electrons to move through this lamp so they will lose more energy. Lamp A will therefore be brighter than lamp B.”

Write a correct explanation. (5)

Answer 9

• lamp B will be brighter as in a parallel circuit voltage is the same for each branch
• lamp A and b have the same voltage, however as lamp B has a lower resistance (and same voltage as lamp A) it has a greater current, current splits at junctions.
• producing more power (p=VxV/R) - high R= low power, in lamp B
• each electron loses the same energy
• more electrons at lamp B, hence greater total energy lost