Quiz 2: Physics 161 Name:_________________________

Summer I’02

E. Gortcheva

1. You throw a ball up in the air and hold your hand under it to catch it when it comes down. The reason why the ball stops is because

a. your hand is there: your hand exerts no force on the ball.

b. your hand exerts a force on the ball perpendicular to its velocity.

c. your hand exerts a force on the ball in the direction of its velocity.

d. your hand exerts a force on the ball in the direction opposite to its velocity.

e. your hand and the ball exerts forces in the same direction on each other.

2. In order to jump off the floor, the floor must exert a force on you

a. in the direction of and equal to your weight.

b. opposite to and equal to your weight.

c. in the direction of and less than your weight.

d. opposite to and less than your weight.

e. opposite to and greater than your weight.

3. A race car starts from rest on a circular track of radius 400 m. Its speed increases at the constant rate of 0.5 m/s . At the point where the magnitudes of the radial and tangential accelerations are equal, determine (a) the speed of the race car, and (b) the elapsed time.