P4.1

Question 1

1. What is the equation for average speed?

Answer 1

-speed (m/s) = distance travelled (m) / tIme taken (s)

Question 2

2. What is the difference between average speed and instantaneous speed for examples of motion where speed is changing?

Answer 2

• average speed: how much distance an object covers over a certain time span (doesn’t tell you exact motion at certain points)
• instantaneous speed: an average over a short time interval, tells you the exact speed the object is moving at, at an instant in time

Question 3

3. What is the displacement of an object at a given moment?

Answer 3

• its distance from its starting point with an indication of direction
• displacement can be positive or negative depending on its direction

Question 4

5. What does the gradient of a distance-time and displacement-time graph tell us?

Answer 4

• Distance-time graph: gradient= speed

- Displacement-time graph=velocity

Question 5

5. What happens as the gradient gets steeper in a distance/displacement-time graph?

Answer 5

-the steeper the gradient, the faster the object is going (higher speed)

Question 6

6. How do you calculate a speed from the gradient of a straight section of a distance-time graph?

Answer 6

Speed= gradient= vertical/horizontal= distance/time

Question 7

8. What does acceleration mean in many everyday situations?

Answer 7

-the change in speed of an object in a given time interval

Question 8

8. What is deceleration?

Answer 8

-negative acceleration (if something slows down the change in velocity will be negative)

Question 9

9. What is the instantaneous velocity of an object?

Answer 9

-its instantaneous speed with an indication of the direction

Question 10

10. What happens to velocity if an object moves in the opposite direction?

Answer 10

• the velocity of an object moving in a straight line is positive if it is moving in one direction and negative if it is moving in the opposite direction
• a line can have the same speed but a different velocity

Question 11

12. How do you calculate the acceleration from the gradient of a velocity–time graph (or from a speed-time graph in situations where direction of motion is constant)?

Answer 11

Acceleration= gradient=horizontal/vertical

Question 12

13. What is the equation for acceleration?

Answer 12

Acceleration (m/s2) = change in velocity (m/s) / time taken (s)