9. A car driver brakes gently. Her car slows down front -- deceleration?
10. A train slows down from 60m/s to 20m/s in 50s.
a) What is its acceleration?
b) Write your answer in words?
11. The acceleration of car is 10m/s. If the car starts from rest,
a) What will be its speed after 10s?
b) How long it takes to reach a speed 1000m/s?
12. A sprinter has an acceleration of 5m's during the first 2 seconds of the race. What
velocity does she reach after this time?
13. A train increases its velocity from 6m/s to 10m/s. Calculate its acceleration?
14. A car travelling at 20m/s slows down to 10m/s in 25. Calculate its acceleration?
15. Leaving bus stop, the bus reaches a speed of 8m/s after 10s. What is its acceleration?

9) This is a case of deceleration

10)-0.8 ms-2

b) acceleration is the change in velocity with time

11)

a) 100 ms-1

b) 100 seconds

12) 10ms-1

13) more information is needed to answer the question

14) - 0.4 ms^-2

15) 0.8 ms^-2

Explanation:

The deceleration is;

v-u/t

v= final velocity

u= initial velocity

t= time taken

20-60/50 =- 40/50= -0.8 ms-2

11)

Since it starts from rest, u=0 hence

v= u + at

v= 10 ×10

v= 100 ms-1

b)

v= u + at but u=0

1000 = 10 t

t= 1000/10

t= 100 seconds

12) since the sprinter must have started from rest, u= 0

v= u + at

v= 5 × 2

v= 10ms-1

14)

v- u/t

10 - 20/ 25

10/25

=- 0.4 ms^-2

15)

a=v-u/t

From rest, u=0

8 - 0/10

a= 8/10

a= 0.8 ms^-2

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