# Dynamics and Space Whole Unit Flashcards

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

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

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

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.

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.

What is speed?

Distance travelled per second.

What is acceleration?

change in velocity per second.

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

The velocity increases by 15ms^{-1} every second.

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

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

What does this speed-time graph show?

Constant speed

What does this speed-time graph show?

Constant acceleration

What does this speed - time graph show?

Constant de-acceleration

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

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

What is a balanced force?

Equal forces acting in opposite directions

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

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

The forces are balanced

What causes friction?

Two surfaces rubbing together

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

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

What is meant by streamlining?

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

Describe a streamlined shape

- Low to the ground
- Smooth
- Have curves

What will an unbalanced force cause?

Acceleration

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)