Dynamics and Space Whole Unit Flashcards Preview

Harris Academy N4 Physics > Dynamics and Space Whole Unit > Flashcards

Flashcards in Dynamics and Space Whole Unit Deck (64)
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1

Describe how to measure average speed.

  • Mark a start line and a finish line.
  • Measure the distance between the start and finish line with a ruler/metre stick.
  • Start a stopwatch when the object crosses the start line and stop it when the object crosses the finish line.
  • Calculate the average speed = distance between start and finish / time on stopwatch

2

Describe how to measure average speed using the equipment below.

 

  • Two light gates are connected to a timer.
  • The car rolls down the slope.
  • When the cardboard breaks the first lightgate beam it starts the timer. When the cardboard breaks the second lightgate beam it stops the timer.
  • The timer records the time taken to go from the first to the second light gate.
  • Measure the distance between the two light gates using a metre stick.
  • Calculate the speed = distance between light gates / time on timer

3

Explain how to use the equipment below to calculate the instantaneous speed of the car.

  • Measure the length of the cardboard using a ruler.
  • Roll car down the slope.
  • When the cardboard breaks the beam it starts the timer connected to the light gate. When the cardboard has passed through the beam is remade and the timer stops.
  • Speed = length of cardboard / time on timer

4

Explain the difference between average and instantaneous speed.

Average speed is over a long period of time, Instantaneous speed is the speed over a very short period of time.

5

What is the difference between a vector and a scalar quantity?

A scalar needs size/magnitude to be described correctly. A vector needs size/ magnitude and direction to be described correctly.

6

What is speed?

Distance travelled per second.

7

What is acceleration?

change in velocity per second.

8

What is meant by an acceleration of 15ms-2 ?

The velocity increases by 15ms-1 every second.

9

Explain how to measure the acceleration of the car using the equipment shown below and a stop watch.

  • Car starts from rest so u = 0ms-1.
  • When the car is released start the stop watch when it reaches the light gate stop the stop watch.
  • This is t, the time for the change in velocity.
  • When the cardboard passes through the light gate the timer attached to it records this time.
  • Measure the length of the card with a ruler.
  • The final velocity, v = length of card / time on timer
  • Then calculate acceleration, a = (v-u)/t

10

Explain how to measure acceleration using the equipment shown below and a stop watch.

  • When the cardboard passes through the first light gate the timer attached to it records this time.
  • Measure the length of the card with a ruler.
  • The initial velocity, u = length of card / time on timer
  • As the car rolls down the ramp, start the stop watch when it reaches the first light gate and when it reaches the second light gate stop the stop watch.
  • This is t, the time for the change in velocity.
  • When the cardboard passes through the second light gate the timer attached to it records this time.
  • The final velocity, v = length of card / time on timer
  • Then calculate acceleration, a = (v-u)/t

11

What does this speed-time graph show?

Constant speed

12

What does this speed-time graph show?

Constant acceleration

13

What does this speed - time graph show?

Constant de-acceleration

14

Describe how to calculate acceleration from a veocity - time graph.

  • Pick two pints on the slope.
  • work out the change in speed,
  • t = time to go from the initial to the final speed.
  • Then use a = ∆v/t

15

What are the three effects a force can have?

  • Change the speed of the object
  • Change the direction of travel of the object
  • Change the shape of the object

16

What is a balanced force?

Equal forces acting in opposite directions

17

Newtons 1st Law is about balanced forces, what two things can happen if a balanced force acts on an object?

  • Remains stationary
  • Travels at a constant speed in a straight line

18

An object travels at a constant speed of 10ms-1. What can be said about the forces on it?

The forces are balanced

19

What causes friction?

Two surfaces rubbing together

20

How can you increases friction?

  • Increase the area of the rubbing surfaces
  • Make the rubbing surfaces rougher
  • Push the rubbing surfaces togerther more
  • Increase the speed that the surafces are rubbed together

21

How can you decrease friction?

  • Decrease the area of the rubbing surfaces
  • Make the rubbing surfaces smoother
  • Push the rubbing surfaces together less
  • Decrease the speed that the surfaces are rubbed together
  • Lubricate/oil/ wax the surfaces
  • Streamline the object

22

What is meant by streamlining?

Streamlining is changing the shape of an object to reduce air/water resistance

23

Describe a streamlined shape

  • Low to the ground
  • Smooth
  • Have curves

24

What will an unbalanced force cause?

Acceleration

25

Explain how a seatbelt works in terms of Newton's Laws.

  • When a car travels at a constant velocity the forces on it are balanced. (Newtons 1st Law)
  • If the brakes are applied they provide an unbalanced force that stops the car. (Newtons 2nd Law)
  • The passengers continue to travel at a constant speed in a straight line. (Newtons 1st Law)
  • The seatbelt provides an unbalanced backwards force to decelerate the passenger to zero without hitting the windscreen. (Newtons 2nd Law)

26

What is the difference between mass and weight?

Mass is a measure of the partcles that make an object up. Weight is a force caused by the gravitational field strength of a planet.

27

What is meant by gravitational field strength?

Force per unit mass

28

An astronaut has a mass of 50kg. What will happen to the astronauts mass on the Moon?

It stays at 50kg. Mass does not change.

29

An astronaut has a mass of 50kg. What will happen to the astronauts weight on the Moon?

The weight will decrease as there is a lower gravitaional field strength on the Moon.

30

Describe how a cyclist can streamline themself

  • Crouch over the handlebars
  • Wear tight lycra clothing
  • Specially shaped helmet