P5-forces

Question 1

what is the definition of acceleration

Answer 1

the change in velocity in a time period

Question 2

equation for acceleration?

Answer 2

acceleration (m/s^2) =change in velocity(m/s) / time (s)

Question 3

difference between speed and velocity?

Answer 3

speed is how fast you’re going. Velocity is speed in a given direction

Question 4

what is the typical speed of a person walking?and a person running?

Answer 4

1.5m/s and 3m/s

Question 5

average speed of a person cycling?

Answer 5

6m/s

Question 6

average speed of: a car, a train and a plane

Answer 6

25m/s, 55m/s and 250m/s

Question 7

what does the gradient of a distance time graph show?

Answer 7

the speed

Question 8

what does a flat section of a distance time graph show?

Answer 8

the object has stopped moving

Question 9

what does an upward curve and a downward curve show on a distance time graph?

Answer 9

acceleration and deceleration

Question 10

what does a straight uphill line show on a distance time graph?

Answer 10

steady speed

Question 11

what does the gradient of a velocity time graph show?

Answer 11

acceleration

Question 12

a flat section of a VT graph shows…

Answer 12

steady speed

Question 13

a straight uphill section of a VT graph shows…

a straight downward line shows…

Answer 13

acceleration and deceleration

Question 14

a curve upwards or downwards on a VT graph shows…

Answer 14

increasing acceleration or deceleration

Question 15

what does the area under a VT graph show?

Answer 15

the distance travelled

Question 16

what increases as the speed of a vehicle increases?

Answer 16

the frictional forces

Question 17

describe terminal velocity for a falling object

Answer 17

at first, the force of gravity is much larger than the frictional force, so they accelerate. then as the speed up, friction increases and this reduces acceleration until the forces are equal. The object has reached its max. speed/ terminal velocity so will fall at a steady speed.

Question 18

what is the accelerating force for all falling objects?

Answer 18

gravity

Question 19

what is terminal velocity determined by?

Answer 19

the object’s drag compared to it’s weight

Question 20

what does the force of friction depend on?

Answer 20

shape and area

Question 21

why does opening a parachute decrease the terminal velocity?

Answer 21

the area of the sky diver will have increased. so air resistance increases, meaning they reach their terminal velocity sooner and at a lower speed.

Question 22

explain Newton’s first law

Answer 22

If the resultant force on a stationary object is zero, the object will stay stationary. If the resultant force on a moving object is zero, it will carry on moving at the same velocity

Question 23

Newton’s second law states that a resultant force applied to an object will cause…

Answer 23

an acceleration in the same direction as the resultant force.

Question 24

resultant force=…?

Answer 24

resultant force (N)= mass(kg) x acceleration (m/s^2)

Question 25

acceleration is directly proportional to what and is indurectly proportional to what?

Answer 25

resultant force and mass

Question 26

what happens when you apply force to an object?

Answer 26

It can stretch, compress or bend

Question 27

Why do you need more than one force to make an object stretch/compress/bend?

Answer 27

If there was only one force, the object would simply move in the direction of the applied force.

Question 28

When a force stretches/compresses an object, _____ is done

Answer 28

work

Question 29

what affect does work being done on an object have on the object’s energy stores?

Answer 29

energy is transferred to the elastic potential energy store.

Question 30

what is elastic deformation?

Answer 30

the object can go back to it’s original shape after the forces have been removed. All the energy from work being done goes to the elastic potential store of the object. Happens in ELASTIC objects.

Question 31

what is inelastic deformation?

Answer 31

the object doesn’t return to it’s original shape or length when the force has been removed.

Question 32

what is the equation linking force applied, spring constant and extension?

Answer 32

Force applied (N) = Spring constant (N/m) x Extension (m)

Question 33

what is the extension of a stretched spring directly proportional to?

Answer 33

the force applied.

Question 34

what does a higher spring constant mean for an object?

Answer 34

It’s a stiffer material.

Question 35

what happens when you reach the limit of proportionality of an object?

Answer 35

the extension is no longer proportional to the force and begins increasing disproportionately.

Question 36

what is the equation for momentum?

Answer 36

momentum (kg m/s) = mass (kg)x velocity (m/s)

Question 37

is momentum a scaler or vector quantity?

Answer 37

a vector quantity. it has size AND direction.

Question 38

What is the conservation of momentum?

Answer 38

in a closed system, the total momentum before an event is equal to the total momentum after.

Question 39

what causes a change in momentum?

Answer 39

a resultant force.

Question 40

what is the equation for a force causing a change in momentum?

Answer 40

force(N)= change in momentum(kg m/s) / change in time (s)

Question 41

what is the rate of change of momentum equal to?

Answer 41

the force causing the change.

Question 42

Why are things liked cars designed to slow people down over a long period of time when they crash?

Answer 42

because if someone’s momentum changes very quickly, the forces on their body will be very large, this is more likely to cause injury.

Question 43

give two examples of cars being designed to have a slow rate of change of momentum:

Answer 43

Crumple zones-crumple on impact, increasing time taken for car to stop seat belts-stretch slightly, increasing time taken for passenger to stop.

Question 44

What happens when a force moves an object through a distance?

Answer 44

energy is transferred, so work is done.

Question 45

what is the equation for work done?

Answer 45

work done (J)= force (N) x distance (m)

Question 46

how many Newton-metres are in 1 joule if work?

Answer 46

1Nm