# Acceleration and constant speed question

1. Jan 30, 2005

### dbzsongoku

Can someone tell me which of the these is true or false and possibly explain it to me?

a)The acceleration of a car is zero when it is turning right at a constant speed
b)The acceleration of a car is zero when it is driving up a long straight incline at constant speed
c)The acceleration of a car is zero when it is topping the crest of a hill at constant speed
d)The acceleration of a car is zero when it is bottoming out at the lowest point of a valley at constant speed
e) The acceleration of a car is zero when it is speeding up as it descends a long straight decline.

Any help would be great.

thanks

2. Jan 30, 2005

### dextercioby

Daniel.

3. Jan 30, 2005

### DB

These are fairly easy questions if you just Think. Consider acceleration as the rate of change in speed, in your case ou can even think of it as a change in speed. Think of forces dependent on inclinations.

4. Jan 30, 2005

### christinono

Make sure you know exactly what acceleration is. In order for an object to accelerate, its velocity must be changing.

5. Jan 30, 2005

### dextercioby

THE VELOCITY VECTOR MUST BE CHANGING WITH TIME AS TO HAVE A NONZERO ACCELERATION VECTOR...

Daniel.

6. Jan 31, 2005

### dbzsongoku

Is this correct?
a) false because direction is changing
b) true
c) true
d) true
e) false because magnitude of the accerlation is changing

7. Jan 31, 2005

### dextercioby

The way i see it,only B is true...

Daniel.

8. Jan 31, 2005

### da_willem

why does your argment for a not apply to c and d?

9. Jan 31, 2005

### HallsofIvy

Staff Emeritus
Unfortunately, thinking THAT way will lead you to the wrong answer to at least one of these. Think "velocity" not "speed"!