If the velocity of an object is zero at one instant,what is true about the acceleration of that object? (There could be more than one correct choice. )
A)The acceleration could be positive.
B)The acceleration could be negative.
C)The acceleration could be zero.
D)The acceleration must be zero.
Under what condition is average velocity equal to the average of the object's initial and final velocity?
A)This can only occur if there is no acceleration.
B)The acceleration is constant.
C)This can occur only when the velocity is zero.
D)The acceleration must be constantly increasing.
E)The acceleration must be constantly decreasing.
A racing car accelerates uniformly from rest along a straight track.This track has markers spaced at equal distances along it from the start,as shown in the figure.The car reaches a speed of 140 km/h as it passes marker 2.
Where on the track was the car when it was traveling at half this speed,that is at 70 km/h?
A)before marker 1
B)at marker 1
C)between marker 1 and marker 2
When a ball is thrown straight up with no air resistance,the acceleration at its highest point
D)reverses from upward to downward.
E)reverses from downward to upward.