Topic 5 – Forces (Post 2018)

Question 1

The student attached the mass holder to the string.
The string rubbed along the edge of the bench as the mass holder fell to the floor.
Suggest what the student could do to prevent the string from rubbing.

Answer 1

use a pulley (on the edge of the bench)

Question 2

Describe the relationship between the resultant force on the trolley and the acceleration of
the trolley.

Answer 2

(directly) proportional

Question 3

Describe how the investigation could be improved to reduce the effect of random errors (pulley + trolley)

Answer 3

repeat the measurements/investigation

ignore anomalies and calculate the mean / average

Question 4

Write down the equation that links acceleration (a), mass (m) and resultant force (F

Answer 4

resultant force = mass × acceleration

Question 5

Explain what is meant by ‘elastically deformed’

Answer 5

will return to its original shape/length

when the force is removed

Question 6

A student investigated the relationship between the force applied to a spring and the extension of
the spring.
Describe a method the student could use to obtain the results given in Figure 2

Answer 6

set up a clamp stand with a clamp
*   hang the spring from the clamp
*   use a second clamp and boss to fix a (half) metre rule alongside the spring
*   record the ruler reading that is level with the bottom of the spring
*   hang a 1 N / a known weight from the bottom of the spring
*   record the new position of the bottom of the spring
*   calculate the extension of the spring
*   measure the extension of the spring
*   add further weights to the spring so the force increases 1 N at a time up to 5 N
*   for each new force record the position of the bottom of the spring and calculate
/ measure the extension
Hazard: Clamp (stand, boss and masses) might fall off desk
Risk: injury to feet
Precaution: Use clamp to fix apparatus to the bench

Question 7

Explain the effect of two other factors on the braking distance of a car

Answer 7

*   poor condition of tyres
*   poor road surface
*   wet or icy road
*   poor/worn brakes
Explanation
*   because of decreased friction
Factors
*   increased mass of car/passengers
Explanation
*   increases kinetic energy of car
*   more work needs to be done to stop car
*   increases momentum of the car
Factor
*   road slopes downhill
Explanation
*   (a component of) gravity opposes the

Question 8

Explain one advantage of using the long ramp compared with using the short ramp (pivot)

Answer 8

the long ramp has a smaller angle
(so) less force is needed

Question 9

The student removed each piece of modelling clay from the oil before dropping the next
piece.
Suggest one reason why.

Answer 9

so that each piece falls the same distance

Question 10

How is the velocity of the aircraft different to the speed of the aircraft?

Answer 10

velocity includes direction

Question 11

Air is taken into the front of the engine and pushed out of the back of the engine.
Explain the effect this has on the engine.

Answer 11

(an equal) force from the air pushes on the engine/aircraft

in the opposite direction

Question 12

Explain the possible dangers caused by a vehicle having a large deceleration when it is
braking.

Answer 12

brakes overheating
allow brake fade
or
brakes locking
allow wheels locking

(causing) loss of control
or
(causing) a skid

Question 13

pressure acts in ___ directions

Answer 13

all