Question

the next 2 questions refer to the diagram below. a man jumps repeatedly on a trampoline that is pulled at a constant speed by a tractor.

1. to a stationary observer on the ground, the man would appear to be moving

a. up and down only.
b. along with the tractor horizontally only.
c. in successive parabolas.
d. zig - zagging up and down repeatedly.

1. to the driver of the tractor, the man would appear to be moving

a. up and down only.
b. not at all.
c. in successive parabolas.
d. wait....no one is driving!

1. which of the following is not a vector quantity?

a. acceleration
b. displacement
c. time
d. velocity

1. in the absence of air resistance, what is the angle that gives the greatest range for an upwardly launched projectile landing on level ground?

a. 15 degrees.
b. 30 degrees.
c. 45 degrees.
d. 60 degrees.
e. 75 degrees.

1. what is the path of a projectile (in the absence of friction)?

a. a wavy line
b. a parabola
c. a hyperbola
d. projectiles do not follow a predictable path.

1. which of the following is an example of projectile motion?

a. a jet lifting off a runway
b. a thrown baseball
c. a parachutist gliding down to earth with her chute open
d. a space shuttle being launched

1. which of the following is a physical quantity that has both magnitude and direction?

a. vector
b. scalar
c. resultant
d. frame of reference

Explanation:

1. The man on the trampoline moving with the tractor has a vertical jumping motion and a horizontal motion with the tractor. So, to a stationary observer on the ground, he moves in successive parabolas due to the combination of vertical - up - and - down motion and horizontal motion.
2. The driver of the tractor is moving with the same horizontal speed as the man on the trampoline. So, to the driver, the man only appears to move up and down.
3. Time has only magnitude and no direction, so it is a scalar, not a vector.
4. The range formula for a projectile launched on level ground is $R=\frac{v_{0}^{2}\sin2\theta}{g}$. When $\theta = 45^{\circ}$, $\sin2\theta=\sin90^{\circ}=1$ which gives the maximum range.
5. In the absence of friction, the path of a projectile is a parabola as it has a constant horizontal velocity and a vertical acceleration due to gravity.
6. A thrown baseball is an example of projectile motion as it is in free - fall under gravity after being thrown. A jet lifting off has an upward thrust, a parachutist has air resistance and buoyancy forces, and a space shuttle has thrust during launch.
7. A vector is a physical quantity that has both magnitude and direction.

Answer:

1. c. In successive parabolas.
2. a. Up and down only.
3. c. time
4. c. 45 degrees.
5. b. a parabola
6. b. a thrown baseball
7. a. vector