Our Dynamic Universe

Question 1

Describe an experiment to measure the acceleration of an object down a slope:

Answer 1

Equipment needed:

-two light gates, ti mer, trolley carrying a mask (piece of card) of a known length

Set up apparatus so the trolley runs down the slope and the mask on the trolley cuts the beams of both light gates.

Measurements required:

• length of mask (in metres)
• time to cut first light gate t1 (in seconds)
• time between light gates t2 (in seconds)
• time to cut second light gate t3 (in seconds)

Calculati on:

• Determine the ini al and final velocity using v = mask length/ time to cut light gate beam.

-Determine the accelera on using: a= (v-u)/t

Question 2

State the appropriate relationship to find average speed:

Answer 2

v = d/t

Question 3

State the appropriate relationship to find average velocity:

Answer 3

v = s/t

Question 4

Define terminal velocity:

Answer 4

When an object is in free-fall, the weight of the object accelerates the object downwards. If the object is falling through the air then the air fric tion on the object will increase as the object gets faster.

Eventually the weight and the air friction forces will balance causing the object to stop accelerating downwards and instead fall with a constant speed (as Newton’s 1st Law states)

This maximum constant velocity that is achieved is called the “Terminal Velocity”

Question 5

Define free fall:

Answer 5

When falling, with the absence of air resistance, all objects fall with the same acceleration of -9.8ms^-2, regardless of their mass, since the only force acting on them is the gravitational field strength. This is because an objects acceleration due to gravity is always -9.8ms^2.

Question 6

Define apparent weight:

Answer 6

Apparent weight is a measure of downwards force.

Question 7

Define vector addition:

Answer 7

Vector addition is the operation of adding two or more vectors together into a vector sum.

Question 8

Describe how to calculate the displacement and acceleration from a v-t graph:

Answer 8

Area under graph = displacement

Gradient = acceleration

Question 9

Suvat equation of motion (no t):

Answer 9

v^2 = u^2 + 2as

Question 10

Suvat equation of motion (no v):

Answer 10

s = ut + 1⁄2at^2

Question 11

Suvat equation of motion (no s):

Answer 11

v = u + at

Question 12

Suvat equation of motion (no a):

Answer 12

s = 1/2(u + v)t

Question 13

State Newton’s first law:

Answer 13

An object will remain at rest or move with a constant speed unless acted upon by an un- balanced force.

Question 14

State Newton’s second law:

Answer 14

The accelera tion (a) of an object is directly propor tional to the unbalanced force (Fun) acti ng on it and inversely propor onal to its mass (m). An object will accelerate if acted upon by an unbalanced force.

Question 15

State Newton’s third law:

Answer 15

When two objects interact, they exert equal and opposite forces on each other. Every action has an equal and opposite reaction.

Question 16

Define tension:

Answer 16

Tension is the force that occurs when a rope, cord, or similar item pulls on an object.

Question 17

Relationship between force, mass and acceleration:

Answer 17

Fun = ma

Question 18

Relationship between weight, gravitational field strength and mass:

Answer 18

W = mg

Question 19

Relationship between force, work done and distance:

Answer 19

Ew = Fd

Question 20

Relationship between mass, gravitational field strength, height and energy:

Answer 20

Ep = mgh

Question 21

Relationship between velocity, mass and energy:

Answer 21

Ek = 1/2mv^2

Question 22

State the principle of conservation of energy:

Answer 22

Energy cannot be created or destroyed, but can be changed from one form to another.

Question 23

State the principle of conservation of momentum:

Answer 23

The total momentum just before a collision or explosion is equal to the total momentum just a fter the collision or explosion, in the absence of external forces.

Question 24

Use Newton’s third law to explain the motion of objects interacting:

Answer 24

For example, if a person sits on a chair, the person exerts a downward force on the chair and the chair exerts an equal and opposite force on the person.

Question 25

Define momentum:

Answer 25

The momentum of an object is defined as the product of its mass and velocity.

Question 26

Relationship between force, time, initial and final momentum:

Answer 26

Ft = m(v - u)

Question 27

Define impulse:

Answer 27

The force applied to an object mul plied by the time over which the force acts is called the impulse. In addi tion, a force applied to a body will cause a change in velocity and therefore a change in momentum.

Question 28

Relationship between velocity, mass and momentum:

Answer 28

p = mv

Question 29

State the relationship used to explain the horizontal range of a projectile:

Answer 29

vH: cosx = a/h

Question 30

State the relationship used to explain the vertical component of a projectile:

Answer 30

vV = sinx = o/h

Question 31

Define projectile:

Answer 31

A projec tile is an object that has been launched, fired, thrown or is falling through the air.

Question 32

Universal gravitational constant:

Answer 32

Gravita onal Constant = 6.67 x 10^-11 Nm^2Kg^-2

Question 33

Describe and state Newton’s law of universal gravitation:

Answer 33

This theory explains that every body with mass will exert an at rac tive force on every other body with mass. This force is called gravity.

The magnitude of this gravita tional force is dependant on the mass of the two objects, and inversely propor tional to the square of the distance that separates them.

F = (Gm1m2)/r^2

Question 34

Define satellites in terms of free fall:

Answer 34

A satellite in orbit has constant horizontal speed and falls to the Earth with a constant vertical acceleration due to gravity.

Satellites in orbit are therefore considered to be projectiles.

We say that the satellite is in free fall - this means that the only force acting on the satellite is gravity.

Question 35

Description of an experiment to measure the acceleration of a falling object:

Answer 35

Use of the equa tion v=u+at requires:

• length of mask (falling object) l (in metres)
• me to cut first light gate t1(in seconds)
• me between light gates t2(in seconds)
• me to cut second light gate t3(in seconds)

Equipment needed:

-two sets of light gates, timer, falling object

Drop the object so it falls and cuts each light gate.

Initial velocity is calculated using u = length of mask/t1

Final velocity is calculated using v = length of mask/t3

Acceleration is calculated using a = (v-u)/t2

Question 36

Define scalar quantity:

Answer 36

A scalar quan tity is completely defined by stati ng its magnitude.

Question 37

Define vector quantity:

Answer 37

A vector quan tity is completely defined by sta ting its magnitude and direction.

Question 38

Energy and momentum in elastic collisions:

Answer 38

Momentum is conserved.

Kinetic energy is conserved.

Question 39

Energy and momentum in inelastic collisions:

Answer 39

Momentum is conserved.

Kinetic energy is lost.

Question 40

Energy and momentum in explosions:

Answer 40

Momentum is conserved.

Kinetic energy is gained.

Question 41

Describe how to calculate the change in velocity from an a-t graph:

Answer 41

Area under graph = change in velocity

Question 42

Describe how to calculate velocity from an s-t graph:

Answer 42

Gradient = velocity