Sketch the following speed-time graphs:
Determine the:
- Acceleration of the objects
- Distance travelled
1. A Car travels at a steady(constant) speed of 65 km/h for 3 hours.
2. A boy runs from rest and steadily accelerates to a speed of 10 m/s within 5 seconds.
3. A motorcycle accelerates steadily from 12 m/s to 24 m/s over a period of 6 seconds.
4. Car decelerates steadily from a speed of 54 km/h until it stops 6 seconds later.​

Respuesta :

1) Acceleration: 0, distance: 195 km

2) Acceleration: [tex]2 m/s^2[/tex], distance: 25 m

3) Acceleration: [tex]2 m/s^2[/tex], distance: 108 m

4) Acceleration: [tex]2.5 m/s^2[/tex], distance: 45 m

5) Find the speed-time graphs in attachment

Explanation:

1)

The acceleration of an object is given by:

[tex]a=\frac{v-u}{t}[/tex]

where

u is the initial velocity

v is the final velocity

t is the time elapsed

In this problem, the car is travelling at constant speed, so

[tex]v=u[/tex]

and so the acceleration is zero:

[tex]a=0[/tex]

And therefore, we can calculate the distance covered using the equation:

[tex]d=vt[/tex]

where

v = 65 km/h is the speed

t = 3 h is the time

Substituting,

[tex]d=(65)(3)=195 m[/tex]

2)

We calculate the acceleration using the equation:

[tex]a=\frac{v-u}{t}[/tex]

where here we have:

u = 0 is the initial velocity

v = 10 m/s is the final velocity

t = 5 s is the time elapsed

Substituting,

[tex]a=\frac{10-0}{5}=2 m/s^2[/tex]

The distance can be calculated using the suvat equation:

[tex]s=ut+\frac{1}{2}at^2[/tex]

where

u = 0

t = 5 s

[tex]a=2 m/s^2[/tex]

Substituting,

[tex]s=0+\frac{1}{2}(2)(5)^2=25 m[/tex]

3)

Again, we calculate the acceleration using:

[tex]a=\frac{v-u}{t}[/tex]

where this time we have:

u = 12 m/s is the initial velocity

v = 24 m/s is the final velocity

t = 6 s is the time elapsed

Substituting,

[tex]a=\frac{24-12}{6}=2 m/s^2[/tex]

The distance is calculated using the suvat equation:

[tex]s=ut+\frac{1}{2}at^2[/tex]

where

u = 12 m/s

t = 6 s

[tex]a=2 m/s^2[/tex]

Substituting,

[tex]s=(12)(6)+\frac{1}{2}(2)(6)^2=108 m[/tex]

4)

Again, we calculate the acceleration using:

[tex]a=\frac{v-u}{t}[/tex]

where this time we have:

u = 54 km/h = 15 m/s is the initial velocity

v = 0 is the final velocity

t = 6 s is the time elapsed

Substituting,

[tex]a=\frac{0-15}{6}=-2.5 m/s^2[/tex]

The distance is calculated using the suvat equation:

[tex]s=ut+\frac{1}{2}at^2[/tex]

where

u = 15 m/s

t = 6 s

[tex]a=-2.5 m/s^2[/tex]

Substituting,

[tex]s=(15)(6)+\frac{1}{2}(-2.5)(6)^2=45 m[/tex]

5)

The speed-time graph of each situation is shown in attachment. We notice that:

1) In case 1, the car travels at constant speed: this means that the speed-time graph is a horizontal line at v = 65 km/h

2) In case 2, there is a constant acceleration, with the speed changing from 0 to 10 m/s in 5 seconds: this is represented by a line having a slope of 2 (the slope of a speed-time graph corresponds to the acceleration)

3) Similarly, there is a constant acceleration, with the speed changing from 12 m/s to 24 m/s in 6 seconds: this is represented by a line having a slope of 2

4) This time there is a deceleration (negative acceleration), so the slope of the line here is negative.

Learn more about acceleration:

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