Forces and motion Flashcards
Does a distance quantity require a specific direction?
No specific direction is required so it is a scalar quantity?
If an object moves 3 meters to the left and then 3 meters back to its initial position, what is the object’s total displacement?
- The object has 0 displacement.
- Displacement is a vector quantity so it also involves direction.
- The object starts and ends at the same point.
State a typical value for the speed of sound
330 m/s.
What is the typical value for walking speed?
1.5 m/s.
What is a typical value for human running speed?
3 m/s.
What is a typical value for human cycling speed?
6 m/s.
State the equation linking distance, speed and time. Give appropriate units
Distance = speed x time
Distance (m), speed (m/s), time (s).
Why can an object travelling at a constant speed in a circle not have a constant velocity?
- Speed is a scalar quantity.
- Velocity is a vector quantity which means it can only be constant if the direction is constant.
- In circular motion, the direction is continuously changing.
How can speed be calculated from a distance-time graph?
The speed is equal to the gradient of the graph.
What must be done to calculate speed at a given time from a distance-time graph for an accelerating object?
- Drawing a tangent to the curve at the required time.
- Calculating the gradient of the tangent.
State the equation for the average acceleration of an object. Give appropriate units
Acceleration = (change in velocity) / (time taken)
Acceleration (m/s²), velocity (m/s), time (s).
How can distance travelled by an object be calculated from a velocity-time graph?
It is equal to the area under the graph.
Give an approximate value for the acceleration of an object in free fall under gravity near the earth’s surface
9.8 m/s².
What can be said about the resultant force acting on an object when it is falling at terminal velocity
- The resultant force is zero.
- When at terminal velocity, the object is moving at constant speed and so isn’t accelerating.
State newton’s first law for a stationary object
If the resultant force on a stationary object is zero, the object will remain at rest.