Please help me with these Physics questions

Question

Please help me with these Physics questions

Use the picture to determine the slope during phase B. Remember slope=m=(rise/run​)

a. -2m/s

b. 1.5m/s

c. 2m/s

d. 0 m/s

Now observe this graph. What do you notice about the distance covered each second? 

a. it increases throughout

b. the object remains constant as it goes up hill

c. it remains constant throughout

d. it decreases throughout

Use the picture to describe the motion during phase C.

a. object leaves the origin at a constant

b. object is stationary

c. object is going up hill at a constant rate

d. object returns to the origin at a constant rate

e. object leaves the origin at a changing rate

In 1991, four English teenagers built an electric car that could attain a speed of 30.0 m/s. Suppose it takes 9 s for this car to accelerate from 7 m/s to 29 m/s. What is the magnitude of the car's acceleration?

Please respond with the numerical value for the units of m/s^2 do not provide the unit. Also, please round to the nearest whole number. 

Answer 1

Hey Taylor,

Here are some things that might help:

1. Velocity is equal to the change in displacement divided by time.
2. This means that, if you have a displacement vs time graph, the velocity is the slope of that graph
3. An upwards slope represents a positive velocity
4. A slope of 0 means that the position/displacement is not changing - velocity is 0.
5. A downwards slope represents a negative velocity
6. Acceleration is the change in velocity divided by time.
7. If you had velocity vs. time graphs (which you don't have here), the same pattern would apply, but we'd be talking about knowing the acceleration based on the velocity graph, rather than knowing velocities from the displacement graph
8. Straight lines have constant slopes, but curved lines have changing slopes.
9. So, let's look at that 2nd picture
10. We know the velocity is positive because the slope is clearly positive, but we also know that the velocity must be changing because the line is curved.
11. If the slope is increasing, that means velocity is increasing, which is the same as saying that the acceleration is positive.
12. You can tell if a slope is increasing if it's part of a smiley face
13. If the curve instead looks like part of a frown, the slope is decreasing.

To solve your math problem, go back to your definition of acceleration: change in velocity divided by change in time. Find the difference between those two velocities and divide by the time it took for the car to get from one velocity to the other.