# Determine from the graph the speed of the car

• songoku
In summary, the conversation discusses a toy car with a wound spring that exerts a force on a horizontal surface. The graph of force vs time is plotted and the speed of the car after 8 seconds is determined using the area under the graph. The car then collides with a stationary car and the speed of the two cars after collision is calculated using the conservation of momentum equation. The collision is determined to be perfectly inelastic.
songoku

## Homework Statement

A toy car of mass 0.5 kg works with a wound spring that exerts a force as shown in the table below.The car was initially at rest. The spring is wound at the car set in motion on a horizontal surface.

t = 0 s ------> F = 0.2 N
t = 1 s ------> F = 0.18 N
t = 2 s ------> F = 0.15 N
t = 3 s ------> F = 0.12 N
t = 4 s ------> F = 0.1 N
t = 5 s ------> F = 0.08 N
t = 6 s ------> F = 0.05 N
t = 7 s ------> F = 0.02 N
t = 8 s ------> F = 0 N

a. Plot the graph of force vs time using the table above. Determine from the graph the speed of the car 8 s after being released.

b. The car then crashes into a stationary car of mass 1.5 kg and is stuck to the second car. Calculate the speed of the two cars after collision. Show if the collision is elastic or not

## Homework Equations

1. p = Ft
2. conservation of momentum

3. attempt at a solution
a.

I'm not sure how to find the speed from the graph. The best I can try is I assume the graph is triangle, then I find the area which is equal to change in momentum.

Area = change in momentum
0.5*0.2*8 = mv
v = 1.6 ms-1

b. m1u1+m2u2=(m1+m2)V
0.5*1.6 = (0.5 + 1.5) V
V = 0.4 ms-1

The collision is perfectly inelastic

Am I right ?

Thanks

your theory looks correct to me.

Hi rock.freak667

Thanks a lot !

## 1. What is the definition of speed in the context of a car?

Speed is defined as the rate at which an object, in this case a car, is moving. It is typically measured in units of distance per unit of time, such as miles per hour or kilometers per hour.

## 2. How is the speed of a car determined from a graph?

The speed of a car can be determined from a graph by looking at the slope of the line. The steeper the slope, the faster the car is moving. Additionally, the units of the y-axis can indicate the speed, such as distance over time.

## 3. Is the speed of a car constant or does it vary?

The speed of a car can vary depending on the conditions, such as traffic, road conditions, and the driver's actions. However, if the car is traveling at a constant speed, the graph will show a straight line with a constant slope.

## 4. Can the speed of the car be negative?

Yes, the speed of a car can be negative if it is moving in the opposite direction of the positive direction on the graph. For example, if the car is traveling west but the graph is showing movement to the east, the speed would be negative.

## 5. How can the speed of a car be calculated from a graph?

The average speed of a car can be calculated by dividing the total distance traveled by the total time taken. To calculate the speed at a specific point on the graph, the slope of the tangent line at that point can be used.

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