physics - forces (including newtons first and second law)

Question 1

Explain the difference between scalar and vector quantities

Answer 1

• scalar quantities have magnitude (size) only, while vector quantities have magnitude AND direction

Question 2

gives 4 examples of scalar quantities

Answer 2

1. distance
2. speed
3. mass
4. time

Question 3

give 4 examples of vector quantities

Answer 3

1. displacement
2. velocity
3. force
4. acceleration

Question 4

explain the difference between speed and velocity

Answer 4

speed is a scalar quantity, as it shows just how fast, while velocity is a vector quantity, as it shows how fast and the direction it travels in

Question 5

whats resultant force?

Answer 5

it is the overall force acting on an object, found by combining all the forces acting on it

Question 6

to find the forces in the same direction, what do you do?

Answer 6

you add them together

Question 7

to find the forces in the opposite direction, what do you do?

Answer 7

you subtract them

Question 8

how do you know if a force is balanced?

Answer 8

forces are balanced when all the forces acting on an object cancel each other out, so the resultant force is zero

Question 9

give an example of when forces are balanced

Answer 9

when a stationary object stays still, as there is no overall resultant force acting on the object

Question 10

when are forces unbalanced?

Answer 10

forces are unbalanced when the forces acting on an object do not cancel out, so the resultant forces is not zero

Question 11

give an example of when forces are unbalanced

Answer 11

when the object changes its motion, a it may start to move, or speed up, which will cause a non-zero resultant force to produce acceleration, creating an unbalanced force

Question 12

Describe the difference between displacement and distance

Answer 12

distance is a scalar quantity, as it has magnitude only, no direction, while displacement is a vector quantity, as it has magnitude and direction

Question 13

what is a force? (3)

Answer 13

• a force is a push or a pull acting on an object
• its measured in newtons (N)
• force is a vector quantity, meaning it has magnitude and direction

Question 14

can you give 4 examples of contact forces, with explanations to what they are:

Answer 14

1. friction - resists motions between surfaces
2. normal contact force - supports an object from a surface
3. tension - in ropes or strings
4. air resistance - force from air acting opposite to motion

Question 15

give 3 examples of non-contact forces

Answer 15

• gravitational force (weight)
• magnetic force
• electrostatic force

Question 16

in vector force diagrams, what does the length represent and what does the direction represent?

Answer 16

length - magnitude
direction - where force is acting

Question 17

what is the rate of doing work called? (HINT: there is a reason that bosses become bosses and get lots of power - its because they work hard)

Answer 17

power

Question 18

what is Newtons first law?

Answer 18

An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by a resultant (unbalanced) force.

Question 19

give an example to prove newtons first law

Answer 19

Passengers in a car move forward when the car breaks suddenly because their bodies want to remain in motion

Question 20

what is Newtons second law ?

Answer 20

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass

Question 21

give an example to prove newtons second law

Answer 21

Pushing a car requires more force than pushing a bicycle to achieve the same acceleration because the car has a much higher mass - reflects the idea that a larger mass requires a larger force to act upon it