Physics Test Revision

Question 1

What is Inertia?

Answer 1

Inertia is the natural tendency of an object to maintain its velocity, meaning it resists any changes in speed or direction. Inertia is not a force.

Question 2

What is velocity?

Answer 2

An object’s speed and direction.

Question 3

Examples of Inertia.

Answer 3

An object at rest tends to stay at rest. A moving object tends to keep moving with the same speed in the same direction.

Question 4

What is a force?

Answer 4

A push, applying force to move an object away from the source of the force (button), pull applying force to move an object closer to the source (door) or twist combination of push and pull causing rotation (steering wheel).

Question 5

What is net force?

Answer 5

The total forces acting on a single object

Question 6

How do you find net force?

Answer 6

Add any forces acting in the same direction and subtract any forces acting in opposite directions. In answer write if its to the left or right

Question 7

What are the units of force and net force?

Answer 7

Newtons

Question 8

What are balanced forces?

Answer 8

When two forces have the same strength but opposite directions, meaning net force is 0.

Question 9

What are an unbalanced forces?

Answer 9

Unbalanced forces mean forces are different strengths or are acting in the same direction, meaning they can’t cancel out and net force cannot equal 0. This results in the change of an objects velocity.

Question 10

What happens to an object with 0 net force?

Answer 10

It either remains at rest or keeps moving with the same velocity, it has 0 acceleration.

Question 11

What happens to an object with a net force acting on it?

Answer 11

It accelerates in the direction of the net force.

Question 12

What is Newton’s second law?

Answer 12

An object’s acceleration is directly proportional to the force applied and inversely proportional to its mass.

Question 13

If you double or halve force

Answer 13

You will do the same to acceleration and vice versa.

Question 14

If you double/halve mass

Answer 14

You will do the opposite for acceleration. If you double mass acceleration is halved.

Question 15

Standard units for calculation

Answer 15

1 N = 1 kg x 1 m/s/s

Question 16

What do you do when you have smaller units?

Answer 16

When your units are small like this 1 mN = 1 g x 1 m/s/s you convert to N and kg for the formula to work 0.001 N = 0.001 kg x 1 m/s/s.

Question 17

Formula linking force, acceleration and mass

Answer 17

F/a=m F/m=a Mxa=f

Question 18

Why is different acceleration produced on objects with different masses?

Answer 18

Net force produces different accelerations on objects with different masses because the objects have different amounts of inertia. More mass = more inertia and force required to accelerate

Question 19

Why does the acceleration of a rocket change as it rises through the atmosphere, given the thrust exerted by its engines doesn’t change?

Answer 19

The rocket is decreasing mass as it burns fuel to continue moving, the fuel load decreases, thus so does its weight. There is also a decrease in downward forces because a rockets acceleration depends on its net force, although the upward thrust force doesn’t change, the downward forces of gravity and air resistance get weaker because of the thinner atmosphere and being further away from Earth’s centre.

Question 20

What is Newton’s third law of motion?

Answer 20

If one object exerts force on another, the second exerts a force of the same size back. It also says every force has an equal and opposite reaction force/partner.

Question 21

What are the requirements for forces to be paired under Newtons third law?

Answer 21

That a force is paired with another force called a reaction force.
The two forces must, be equal in size, be opposite in direction, be of the same type and act on different objects, to be paired under Newtons third law.

Question 22

If forces have the same strength under Newton’s third law wouldn’t they cancel each other out?

Answer 22

That is only applied when they act upon the same object, pairs of forces always act on different objects and therefore can never be balanced.

Question 23

Why is it that when a person kicks a ball the ball accelerates, yet they don’t?

Answer 23

When a person kicks a ball, they exert a force on the ball — and according to Newton’s Third Law, the ball exerts an equal and opposite force back on the person. But, because the ball has much less mass, it accelerates significantly, while the person’s much larger mass means their acceleration is so small it’s barely noticeable. This difference in acceleration is explained by Newton’s Second Law: the same force causes a greater acceleration in objects with less mass

Question 24

What is gravity’s acceleration?

Answer 24

10m/s/s

Question 25

What is the relationship between velocity and acceleration?

Answer 25

When velocity changes there is acceleration, when it doesn't there isn't

Question 26

What is the relationship between velocity and Newton's second law?

Answer 26

Newton's Second Law says net force changes velocity.

Question 27

What is friction?

Answer 27

A force that resists an object's motion

Question 28

How do forces describe interactions between two objects?

Answer 28

A force is exerted on one object by another.

Question 29

Why can't objects maintain their constant motion (inertia) on Earth forever?

Answer 29

Because forces like gravity, air resistance and friction slow down moving objects by acting in the opposite direction.

Question 30

Purpose of free body diagrams

Answer 30

They show all the forces acting on an object.

Question 31

If forces have the same strength under Newton’s third law wouldn’t they cancel each other out if the objects had the same mass?

Answer 31

Lets say there are two ice skaters with the same mass. They push off each other with their hands and move in opposite directions.Skater A exerts a force on Skater B (action). Skater B exerts an equal and opposite force on Skater A (reaction). Because both skaters have equal mass and feel equal forces, their accelerations are equal in magnitude but opposite in direction and therefore the forces don't cancel each other out.

Question 32

Describe how a deflating balloon moves using Newton's laws.

Answer 32

As air is pushed out of the balloon (action), the balloon experiences an equal and opposite force (reaction). This reaction force pushes the balloon in the opposite direction, causing it to accelerate forward.

Question 33

Using newton's laws how can a swimmer push through water?

Answer 33

When a swimmer pushes against the water with their arms and legs (the action), the water pushes back with an equal and opposite force (the reaction). This reaction force propels the swimmer forward through the water, allowing them to swim. The harder they push against the water, the stronger the reaction force, and the faster they can move.

Question 34

Why can the dog pull the cart despite Newton's third law?

Answer 34

The dog and cart exert equal and opposite forces on each other. The key factor is friction: the dog’s force on the ground creates friction, allowing it to move forward. The cart’s wheels reduce friction, making it easier for the dog to pull. The reduced friction and action-reaction forces allow the dog to pull the cart.

Question 35

Why does an astronaut feel weightless even though gravity is acting on them?

Answer 35

The astronaut is in free fall, accelerating toward Earth at the same rate. With no support force acting on the astronaut, they feel weightless even though gravity is still pulling them down.

Question 36

Weight is equal to

Answer 36

mass x gravitational field strength

Question 37

Why don’t we always notice forces like gravity, friction, or air resistance acting on us?

Answer 37

Because they are often balanced by other forces or are too small to notice at low speeds.