Need For Speed Unit Flashcards
What does this speed-time graph show?

Constant velocity
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
Describe how a cyclist can streamline themself
- Crouch over the handlebars
- Wear tight lycra clothing
- Specially shaped helmet
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
What is acceleration?
Acceleration is the rate of change of speed or the change in speed per second.
Which line on the graph represents the largest acceleration?

Blue Line - it is the steepest
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.
What is speed?
Distance travelled per second.
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.
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.
What is meant by gravitational field strength?
Force per unit mass
What is meant by an acceleration of 15ms-2 ?
The velocity increases by 15ms-1 every second.
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 will an unbalanced force cause?
Acceleration
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 the area under this speed - time graph give?

The distance travelled.
How can a space rocket be slowed down in space?
Reverse the thrusters to provide an unbalanced force backwards to slow you down.
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
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 does this speed-time graph show?

Constant acceleration
What is meant by streamlining?
Streamlining is changing the shape of an object to reduce air/water resistance
An object travels at a constant speed of 10ms-1. What can be said about the forces on it?
The forces are balanced
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)




