P8: Forces

Question 1

what is a

scalar?

Answer 1

quantities that only have MAGNITUDE

Question 2

what is a

vector?

Answer 2

have both MAGNITUDE and DIRECTION

Question 3

WHAT IS

WEIGHT AND MASS?

Answer 3

weight: force acting on an object due to gravitational attraction.
MASS: amount of matter in object

Question 4

weight equn?

Answer 4

w=mg

Question 5

what is

resultant force? and what does it determine?

Answer 5

single force that describes all forces operating on an object
determines:
- direction of objects
- magnitude of force on object

Question 6

work done equn?

Answer 6

w=fd

Question 7

what is newton’s first law?

Answer 7

object remains at rest, or move with constant velocity unless acted upon by resultant force

Question 8

what is newton’s second law?

Answer 8

the accelleration of object is proportional tp resultant force acting upon it and inversely proportional to object’s mass

Question 9

what is newton’s third law?

Answer 9

every action, has an equal and opoosite reaction

Question 10

acceleration eqn?

Answer 10

f=ma

Question 11

what is inertia?

Answer 11

the tendency of an object to continue in its state of rest /at a constant speed unless acted upon by an external force

Question 12

what is inertail mass? and equn?

Answer 12

property of an object that describes how difficult it is to change its velocity
inertial mass= force/acceleration

Question 12

what is inertail mass? and equn?

Answer 12

property of an object that describes how difficult it is to change its velocity
inertial mass= force/acceleration

Question 13

pressure in liquid equn?

Answer 13

pressure= height of column x density of liquid x gravitational field strength

Question 14

what does size of upthrust depend on?

Answer 14

density of fluid
volume of fluid displaced

Question 15

explain why a car has maximum speed?

Answer 15

• maximum forward force by motor
• as speed increases, air resistance increases
• until air resistance = forward force so car can no longer accelerate

Question 16

why do objects sink?

Answer 16

• weight is greater than upthrust
• greater density than water

Question 17

why does an object float?

Answer 17

weight is equal to upthrust
- density less than water

Question 18

why does atmospheric pressure decrease as altitude increases?

Answer 18

• less molecules of air as altitude increases
• less force over an area

Question 19

what is centre of mass?

Answer 19

point through which the weight of the object acts

Question 20

explain the changing motion of a skydiver in terms of forces acting on a skydiver when falling?

Answer 20

• air resistance is lower than force of weight - ACCELERATES
• as acceleration increases, air resistance increases
• so weight/gravity = air resistance
• he reaches terminal velocity

Question 21

why when jumping from higher altitudes , does the sky diver reach higher speed than if he jumped from lower altitude?

Answer 21

• high altitude means less dense air
• so air resistance on sky diver is less
• so can accelerate for longer before reaching terminal velocity