forces and motion

Question 1

1.03. Explain distance time graphs

Answer 1

.distance on y
.time on x
.gradient represents speed
.if line is flat, object is stationary

Question 1

1.04. What is the relationship between average speed, distance moved and time taken

Answer 1

average speed = distance moved / time taken

Question 1

1.05. How do you investigate the motion of everyday objects such as a toy car or a tennis ball

Answer 1

.use a stop watch and a metre ruler
.mark start and end positions for the known distance
.use a metre ruler to measure the distance
.line up front of car with start point, release and start timer
.move eyes to end point
.stop timer when front of car passes end point
.improve by repeating and averaging
.make sure car starts from stationary
.use average speed equation

Question 1

1.06. What is the relationship between acceleration, change in velocity and time taken

Answer 1

.A = v-u/t
.acceleration = change in velocity / time

Question 2

1.07. Explain velocity time graphs

Answer 2

.time on x
.velocity on y
.gradient represents acceleration
.area under graph represents distance
.if line is flat object is moving at a constant velocity

Question 3

1.08. How do you determine acceleration from a velocity time graph

Answer 3

Using the gradient (gradient = acceleration)

Question 4

1.09. How dpo you determine the distance from a velocity time graph

Answer 4

Area under the line

Question 5

1.10. what is the relationship between final speed, initial speed, acceleration and distance moved

Answer 5

v2=u2+2as

(final speed)2 = (initial speed)2 + (2 x acceleration x distance)

Question 6

1.1. describe the effects of forces between bodies

Answer 6

Forces can act on a body to change the velocity, so the speed, direction or both

Or forces can change the shape of a body, stretching it squishing it or twisting it.

Question 7

1.12. identify different types of force

Answer 7

Gravitational, weight, friction, electrostatic, air resistance (drag), tension (force in a spring), up thrust, lift, thrust

Question 8

1.13. how do vector quantities differ from scalar quantities

Answer 8

scalars are quantities with only magnitude (size)

vectors are quantities with magnitude (size) and direction

Question 9

1.14. what type of quantity is force

Answer 9

Force has a magnitude measured in (N) but it also has a direction, a push or a pull, up, down, left or right. So force is a vector

Question 10

1.15. how do you calculate the resultant force of forces that act along a line

Answer 10

Forces along a line can combine by addition.

Question 11

1.16. what is friction caused by and what does it oppose

Answer 11

Friction is caused by surfaces rubbing. The force always acts in the opposite direction to motion

Question 12

1.17. what is the relationship between unbalanced force, mass and acceleration

Answer 12

f = m x a

force = mass x acceleration

Question 13

1.18. what is the relationship between weight, mass and gravitational field strength:

Answer 13

w = m x g

weight = mass x gravitational field strength

it is 10 on earth

Question 14

1.19. what is the stopping distance of a vehicle is made up of

Answer 14

Stopping distance = Thinking distance + Breaking distance

Question 15

1.20. describe the factors affecting vehicle stopping distance

Answer 15

Thinking distance Affected by:

-Tiredness
-Alcohol
-speed of the car

Braking distance affected by:

-Road conditions
-Tyre conditions
-Brake conditions
-speed of the car
-mass of the car

Question 16

1.21. describe the forces acting on falling objects, (explain why falling objects reach a terminal velocity)

Answer 16

Initially the only force is weight as drag is proportional to velocity. So the object accelerates downwards. As it accelerates the velocity so the drag increases as well. meaning there is a smaller resultant force downwards so a smaller acceleration. Until the object reaches a speed where the drag is equal to the weight meaning there is no acceleration, this velocity is know as terminal velocity.

Question 17

1.22. investigate how extension varies with applied force for helical springs, metal wires and rubber bands

Answer 17

-Set up your apparatus
-Measure the length of your spring without
any hanging masses.
-Hang a mass of 100g on the spring
-Measure the new length of the spring
-Calculate the extension of the spring
-Repeat steps 3-5 for increasing the mass
in increments of 100g
-Take note of your results in the table.

Question 18

1.23. how is the the initial linear region of a force-extension graph associated with Hooke’s law

Answer 18

Hooke’s law is that extension is directly proportional to force applied. This is shown by the straight line on the force-extension graph. Hooke’s law is obeyed as long as the line is straight

Question 19

1.24. describe elastic behaviour as the ability of a material to recover its original shape after the forces causing the deformation have been removed

Answer 19

Elastic behaviour is the ability of a material to recover original shape after the force is removed. in a spring this occurs when the force is lower than the elastic limit. loading and unloading force extension curves can be different as long as it returns to its original shape.

Question 20

1.25. know and use the relationship between momentum, mass and velocity

Answer 20

p = m x v

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

Question 21

1.26. use the idea of momentum to explain safety features

Answer 21

To reduce the force experienced by the passenger you need to extend the time for a passenger to stop in a collision. As force is the change in momentum divided by time.

p=mv

Question 22

1.27. how do you calculate the mass, velocity or momentum of objects

Answer 22

use the conservation of momentum

(momentum of A before collision) + (momentum of B before collision) = (momentum of A and B moving together after the collision)

Question 23

1.28. name the relationship between force, change in momentum and time take

Answer 23

Force is the rate of change of momentum. So Force (N) = change in momentum (kgm/s) / time (s)

F = delta P / T

Question 24

1.29. demonstrate an understanding of Newton’s third law

Answer 24

Every action has an equal and opposite reaction.

E.G - Table pushes down on floor, floor pushes up on table. So table doesn’t accelerate.

Question 25

1.30. what is the relationship between the moment of a force and its perpendicular distance from the pivot

Answer 25

moment = force x perpendicular distance from the pivot

Question 26

1.31. where does the weight of a body act through ?

Answer 26

the centre of gravity

Question 27

1.32. state the principle of moments

Answer 27

The principle of moments states that when the clockwise moments are equal to the anticlockwise moments a body will be in equilibrium.

Question 28

1.33. how does the upward forces on a light beam, supported at its ends, vary with the position of a heavy object placed on the beam

Answer 28

when moments are taken from the right hand side as the block is a greater distance the force from the left hand pivot must be bigger to counteract it. The opposite is true for the left hand side.