Question

1. provide the equation for acceleration.
2. use the acceleration triangle to complete the table:

v = a.t	t =	a =
	25 seconds
100m/s		5m/s²
27km/h	3 hours	km/h²
200m/s	50 seconds
	40 seconds	2m/s²
	10 seconds	10m/s²

1. if a car is moving 66km/h to the north and it round a corner (u - turn), also at 66km/h to the south, does it maintain a constant speed? does it maintain a constant velocity?
2. give an example of an object that experiences a negative acceleration.
3. give an example of an object that has positive velocity and a negative acceleration at the same time.

Explanation:

Step1: Recall acceleration formula

The formula for acceleration is $a=\frac{v - u}{t}$, where $a$ is acceleration, $v$ is final - velocity, $u$ is initial - velocity, and $t$ is time. In the case of constant acceleration starting from rest ($u = 0$), and when we consider the relationship $v=at$.

Step2: Fill the table

1. For the first row: Given $t = 20$ s and $a=10$ m/s², using $v = at$, we have $v=10\times20 = 200$ m/s.
2. For the second row: Given $t = 25$ s, assume $a$ is the same as in the first row ($a = 10$ m/s²), then $v=10\times25 = 250$ m/s.
3. For the third row: Given $v = 100$ m/s and $a = 5$ m/s², using $t=\frac{v}{a}$, we get $t=\frac{100}{5}=20$ s.
4. For the fourth row: Given $v = 27$ km/h and $t = 3$ h, using $a=\frac{v}{t}$, we have $a=\frac{27}{3}=9$ km/h².
5. For the fifth row: Given $v = 200$ m/s and $t = 50$ s, using $a=\frac{v}{t}$, we get $a=\frac{200}{50}=4$ m/s².
6. For the sixth row: Given $t = 40$ s and $a = 2$ m/s², using $v=at$, we have $v=2\times40 = 80$ m/s.
7. For the seventh row: Given $t = 10$ s and $a = 10$ m/s², using $v=at$, we have $v=10\times10 = 100$ m/s.

Step3: Answer question 10

Speed is a scalar quantity. The car has a speed of 66 km/h before and after the u - turn, so it maintains a constant speed. Velocity is a vector quantity. The direction of the car changes from north to south, so the velocity is not constant.

Step4: Answer question 11

An example of an object with negative acceleration is a car braking. When a car brakes, it slows down, and the acceleration is in the opposite direction of its motion.

Step5: Answer question 12

An example of an object with positive velocity and negative acceleration is a ball thrown upwards. As the ball moves upwards (positive velocity), the gravitational force acts downwards, causing a negative acceleration (deceleration) until it reaches its maximum height.

Answer:

v (m/s or km/h)	t (s or h)	a (m/s² or km/h²)
250	25	10
100	20	5
27	3	9
200	50	4
80	40	2
100	10	10

1. Speed: Yes; Velocity: No
2. A braking car
3. A ball thrown upwards