Forces - physics

Question 2

What is a scalar quantity

Answer 2

A quantity with magnitude only and no direction.

Question 3

What is a vector quantity

Answer 3

A quantity with both magnitude and direction.

Question 4

Why is velocity a vector but speed is a scalar

Answer 4

Velocity includes direction but speed does not.

Question 5

A person walks 50 m north then 20 m south what is the displacement

Answer 5

30 m north.

Question 6

Why can displacement be zero even if distance is not zero

Answer 6

Because displacement depends on overall change in position and you may return to the starting point.

Question 7

What is mass

Answer 7

The amount of matter in an object measured in kilograms.

Question 8

Why does mass not change on different planets

Answer 8

Because mass does not depend on gravity.

Question 9

What is weight

Answer 9

The force acting on an object due to gravity.

Question 10

What is the unit of weight

Answer 10

Newtons (N).

Question 11

What is the gravitational field strength on Earth

Answer 11

9.8 N/kg.

Question 12

What does gravitational field strength mean

Answer 12

The force acting on each kilogram of mass.

Question 13

State the equation linking weight mass and gravitational field strength

Answer 13

Weight = mass × gravitational field strength.

Question 14

Calculate the weight of a 60 kg person on Earth

Answer 14

588 N.

Question 15

Why is weight a vector quantity

Answer 15

Because it has magnitude and direction towards the centre of the Earth.

Question 16

Where can the weight of an object be considered to act from

Answer 16

The centre of mass.

Question 17

What is a resultant force

Answer 17

The overall force acting on an object after all forces are combined.

Question 18

What happens if the resultant force is zero

Answer 18

The object remains at rest or moves at constant velocity.

Question 19

State Newton’s First Law

Answer 19

An object remains at rest or moves at constant velocity unless acted upon by a resultant force.

Question 20

State Newton’s Second Law

Answer 20

Force equals mass times acceleration (F = ma).

Question 21

A 5 kg object experiences a 15 N force calculate the acceleration

Answer 21

3 m/s².

Question 22

A 10 kg object accelerates at 4 m/s² calculate the force

Answer 22

40 N.

Question 23

Why does increasing mass reduce acceleration for the same force

Answer 23

Because acceleration is inversely proportional to mass.

Question 24

Two forces at right angles are 6 N and 8 N calculate the resultant

Answer 24

10 N.

Question 25

Why does doubling speed more than double braking distance

Answer 25

Because kinetic energy depends on velocity squared.

Question 26

State the kinetic energy equation

Answer 26

KE = ½mv².

Question 27

Calculate the kinetic energy of a 1000 kg car travelling at 20 m/s

Answer 27

200000 J.