Physics 1750 Quiz 2

N = 39.0, E = 22.5 units.

A vector with value 45.0 units is pointed 30o East of North. What are the North and East components of this vector? a. N = 22.5, E = 39.0 units. b. N = 25.0, 39.0 units. c. N = 39.0, 25.0 units. d. N = 39.0, E = 22.5 units.

all of the above

In linear motion, starting from rest with constant acceleration, the average velocity over a time interval t is: a. v at 0.5t. b. 0.5vfinal. c. All of the other answers. d. 0.5at.

.130m/s2

Suppose two children push horizontally, but in exactly opposite directions, on a third child in a wagon. The first child exerts a force of 75.0 N, the second a force of 90.0 N, friction is 12.0 N, and the mass of the third child plus wagon is 23.0 kg. What is the acceleration of the wagon? a. 1.17 m/s2. b. 0.130 m/s2. c. Not enough information. d. 0.652 m/s2.

is always parallel

The velocity of an object ______ to the path of the object.

an interval in time.

The expression Δt usually means

an interval in the x-direction.

The expression Δx usually means

Gravity pulling the Earth upward.

The force that accelerates falling keys is gravity. What is the equal and opposite force?

the average x-direction velocity in time interval t1 − to

The formula (x1 − xo) / (t1 − to) describes

20.0 N, north.

Two forces are acting on a skater. One is 28.3 N toward the northeast (45° N of E). The other is 20.0 N due west. What is the net force on the skater? a. 400 N (scalar). b. 44.7 N, 27° N of E. c. 20.0 N, south. d. 20.0 N, north.

aM / am = m / M.

Use Newton' law of gravity force between mass M and mass m at separation d, F = GMm / d 2, to find the ratio of the accelerations aM / am. a. aM / am = m / M. b. aM / am = M / m. c. aM / am = Md 2 / Gm. d. aM / am = Gm / Md 2.

Δv / Δt

We may write the average acceleration over a time interval as

The specification of direction as well as value.

What distinguishes the word velocity from the word speed in physics?

Distance and direction from a point of origin.

What is displacement? a. Something that happens when one ball hits another. b. The movement of an object like a ball. c. Only Distance from a point of origin. d. Distance and direction from a point of origin.

a. 1.0 m/s 2. b. 2.0 m/s 2. c. 1.5 m/s 2. d. 2.3 m/s 2.

A Cessna aircraft has a lift-off speed of 30 m/s. What minimum constant acceleration does this require if the aircraft is to be airborne after a take-off run of 225 m?

3.1 s.

A ball is kicked with an initial velocity of 20 m/s in the horizontal direction and 15 m/s in the vertical direction. For how long does the ball remain in the air? a. 1.5 s. b. 3.1 s. c. 1.2 s. d. 2.4 s.

10. s.

A baseball is struck 1.0 meters above the ground and given an initial velocity of 98 m/s, 30o above the horizontal. If it is caught also at 1.0 meters above the ground, for how long was it in the air? a. 20. s. b. 5.0 s. c. 10. s. d. 14. s.

668 N.

A brave but inadequate rugby player is being pushed backward by an opposing player who is exerting a force of 800 N on him. The mass of the losing player plus equipment is 90.0 kg, and he is accelerating at 1.20 m/s2 backward. What force does the winning player exert on the ground to move forward if his mass plus equipment is 110 kg?

692 N

A brave but inadequate rugby player is being pushed backward by an opposing player who is exerting a force of 800 N on him. The mass of the losing player plus equipment is 90.0 kg, and he is accelerating at 1.20 m/s2 backward. What is the force of friction between the losing player's feet and the ground? Remember, the friction force is opposite to the direction of motion. a. 108 N. b. 530 N. c. 692 N. d. 800 N.

20.0 m/s south.

A car initially traveling northeast (45° N of E) at 28.3 m/s takes 6.0 s to turn to the east. After the turn, the car is traveling due east at 20.0 m/s. What is the value and direction of the change in velocity? a. 20.0 m/s north. b. 44.7 m/s at 27° N of E. c. 44.7 m/s at 27° S of E. d. 20.0 m/s east. e. 20.0 m/s south.

868 m/s.

A horizontal rifle shoots a bullet 100 m to a target. During flight, the bullet drops 6.5 cm. How fast was the bullet traveling?

54.9 m

A powerful motorcycle can accelerate from rest to 26.8 m/s (100 km/h) in only 4.10 s. How far does it travels in that time? a. 54.9 m. b. 35.8 m. c. 45.3 m. d. 62.1 m.

66 m

A recessed catapult releases a stone with a speed of 25.5 m/s at 45° from the horizontal, at ground level. How far away from the release point is the stone when it returns to ground level?

3680 N.

A rocket sled accelerates horizontally at a rate of 49.1 m/s2 . Its passenger has a mass of 75.0 kg. Calculate the force the seat exerts against his body.

5.01 .

A rocket sled accelerates horizontally at a rate of 49.1 m/s2 . Its passenger has a mass of 75.0 kg. What is the ratio Fsled / Fgrav for this rider? a. .200 . b. 0.653. c. 5.01 . d. 1.53 .

100 N.

Alex throws a 0.20 kg rubber ball down onto the floor. The ball's velocity just before the impact is 6.0 m/s, and just after is 4.0 m/s. If the ball is in contact with the floor for 0.02 second, what is the magnitude of the average force applied by the floor on the ball? a. 100 N. b. 80 N. c. 60 N. d. 20 N.

1.25 m/s2

An 8.0 kg bowling ball experiences a net force of 10 N. What will be its acceleration?

40.0 km north

An airplane travels northeast (45° N of E) for 28.3 km and then turns to travel northwest (45° N of W) for 28.3 km. What was its total displacement from the start at the end of the flight?

10.7 m/s

An eagle is flying horizontally at a speed of 4.00 m/s when the fish in her talons wiggles loose and falls into the lake 5.00 m below. Calculate the speed of the fish relative to the water when it hits the water. a. 10.7 m/s. b. 10.3 m/s. c. 11.1 m/s. d. 9.9 m/s.

24 N.

George accelerates a 0.4 kg ball from rest to 6 m/s during the 0.10 s in which his foot is in contact with the ball. What average force does he apply to the ball during the kick? a. 40 N. b. 24 N. c. 150 N. d. 0.24 N.

Arbitrarily, for the convenience of the problem.

How do we choose the origin that displacement is measured from?

135 m.

John throws a baseball from the outfield from shoulder height, at an initial velocity of 39 m/s with an initial angle of 30 degrees with respect to the horizontal. The ball is in its trajectory for a total interval of 4.0 s before the third baseman catches it at shoulder-height level (Assume air resistance negligible). What is the ball's horizontal displacement in that time? a. Zero m. b. 135 m. c. 164 m. d. 82 m.

An unobservable force is present, as observed by the acceleration.

Newton's second law states: F = ma. How should we interpret this equation?

The two forces act on different objects.

Newton's third law states that for every force there is an equal and opposite force. If these forces are equal and opposite, why don't they cancel out?

may have components parallel and perpendicular

The acelleration of an object ______ to the path of the object. a. is always parallel b. may have components parallel and perpendicular c. is always perpendicular d. is not related to

Atomic electric fields resist inter-penetration.

What is our present understanding of "contact" forces? a. Atomic electric fields resist inter-penetration. b. Little bumps on object surfaces resist slipping action. c. Protons cannot be pushed close to each other. d. All contact forces can be expressed in terms of the normal force.

Elementary particles exchange force carrier bosons.

What is our present understanding of "field" forces? a. All field forces can be expressed in terms of one field. b. Elementary particles distort the space around them. c. Elementary particles exchange force carrier electrons. d. Elementary particles exchange force carrier bosons.

Weight = gravity force; mass = amount of material.

What is the difference between the terms mass and weight?

A velocity

When we subtract a velocity vector from another velocity vector, the result is:

Electric, Magnetic, Gravitational

Which of the following is an example of the type of force that acts at a distance?

Temperature.

Which of the following quantities is a scalar? a. Acceleration. b. Force. c. Temperature. d. Displacement.

Velocity.

Which of the following quantities is a vector?