Motions and Forces

Question 1

Describe the motion of an object in terms of its position, speed or acceleration.

Answer 1

Motion is described by its position, speed (rate of change of position), and acceleration (rate of change of speed).

Question 2

Make use of the following units for measuring distance (mm, cm, m, km) and be able to convert from one unit to another.

Answer 2

1 km = 1000 m
1 m = 100 cm
1 cm = 10 mm
Practice converting between mm, cm, m, and km.

Question 3

Make use of the following units for measuring time (s, min, h) and be able to convert from one unit to another.

Answer 3

1 hour (h) = 60 minutes (min)
1 minute (min) = 60 seconds (s)
Practice converting between s, min, and h.

Question 4

Convert a time expressed in hours, minutes, seconds into a decimal number of hours and vice-versa.

Answer 4

1 hour = 60 minutes = 3600 seconds.
To convert minutes/seconds to decimals, divide by 60 (e.g., 30 min = 0.5 hours).
To convert decimals back to minutes, multiply the decimal by 60.

Question 5

Calculate average speed in kmh-1 and ms-1 using the equation:

Answer 5

Formula: average speed = distance ÷ time
Example: If distance = 100 km and time = 2 hours, speed = 100 ÷ 2 = 50 km/h.

Question 6

Convert km h-1 into m s-1 and vice-versa (using the supplied formula)

Answer 6

Formula: 1 km/h = (1 × 1000) ÷ 3600 = 0.277 m/s.
To convert m/s to km/h, multiply by 3.6.

Question 7

Calculate the distance travelled, or the time taken, knowing average speed

Answer 7

Distance = speed × time
Time = distance ÷ speed.

Question 8

Interpret and describe the motion represented on a distance-time graph.

Answer 8

Slope/gradient of the graph shows the speed of the object.
Flat line: Object is stationary.
Steep line: Object is moving fast.

Question 9

Plot distance-time graphs from a supplied set of data.

Answer 9

Plot time on the x-axis and distance on the y-axis.

Question 10

Calculate the gradient of a speed-time graph to determine the acceleration.

Answer 10

The gradient of a speed-time graph = acceleration.

Question 10

Calculate the gradient at any point of a distance-time graph to determine the

Answer 10

The gradient = change in distance ÷ change in time = instantaneous speed.

Question 11

Interpret the motion represented on a speed-time graph.

Answer 11

Flat line: Constant speed.
Upward slope: Accelerating.
Downward slope: Decelerating.

Question 12

Calculate acceleration in ms-2

Answer 12

Formula: acceleration = (final speed - initial speed) ÷ time
Measured in m/s².

Question 13

Describe and draw vectors to represent forces acting on an object including driving force, Force due to gravity, normal force and resistance.

Answer 13

Driving force: Moves the object forward.
Gravity: Pulls the object downward.
Normal force: Acts perpendicular to the surface.
Resistance: Opposes motion (friction or air resistance).

Question 14

Determine the net force (∑F) on an object by taking into account all of the forces acting and their directions.

Answer 14

The sum of all forces acting on an object.
Consider both magnitude and direction of forces.

Question 15

Explain that a stationary object, or a moving object with constant speed, has balanced forces acting on it.

Answer 15

A stationary object or an object moving at constant speed has balanced forces (net force = 0).

Question 16

State Newton’s 1st and 3rd Laws of Motion in your own words and provide examples.

Answer 16

1st Law: An object at rest stays at rest, and an object in motion stays in motion unless acted upon by an unbalanced force.
3rd Law: For every action, there is an equal and opposite reaction.

Question 17

Calculate the net force on an object using Newton’s 2nd law: ∑F = ma

Answer 17

Formula: ΣF = ma (Net force = mass × acceleration).

Question 18

Use Newton’s laws to explain the motion of an object. For example, passenger motion during car collisions, sporting collisions and other events.

Answer 18

1st Law (Inertia): In a car crash, passengers keep moving forward at the car’s speed until acted on by seatbelts or airbags.
2nd Law (ΣF = ma): The force on an object depends on its mass and acceleration. In sports collisions, heavier players exert more force.
3rd Law (Action-Reaction): When two objects collide, they exert equal and opposite forces on each other (e.g., cars or players in sports).

Question 19

Explain why friction is needed for people to walk or for cars to move forward.

Answer 19

Friction is necessary to walk or for cars to move forward; it provides the grip needed to avoid slipping.

Question 20

Apply Newton’s laws to explain how seatbelts, airbags, crumple zones and headrests reduce injuries in collisions. (Look into further for more detail)

Answer 20

Seatbelts: Hold passengers in place (1st law).
Airbags and crumple zones: Increase time during impact, reducing force (2nd law).
Headrests: Prevent whiplash by applying a force equal and opposite to the head’s movement (3rd law).