2d Kinematics + Forces

Question 1

True or False: If air resistance is negligible, the acceleration of all projectiles is the same

Answer 1

True

Question 2

If the boat is perpendicular to the river in relative motion, the time is takes the boat to cross is independent of the current

Answer 2

True

Question 3

A car going west turns a corner and goes south at constant speed, what is the acceleration vector?

Answer 3

Southeast

Question 4

In projectile motion, what is the optimal angle for maximum distance?

Answer 4

45 degrees

Question 5

True or False: At the apex of a projectile, its velocity is zero

Answer 5

Its vertical velocity is zero, but its horizontal velocity is not zero

Question 6

You toss a ball straight up, and it falls straight back down. Is the acceleration of the ball at the top zero?

Answer 6

Nah, it is still 9.8m/s^2

Question 7

True or false: Megameters per hour per day is a possible unit of acceleration

Answer 7

Yes, because these units result in m/s^2

Question 8

Does the order in which you add vectors when using the head-to-tail method of vector addition matter?

Answer 8

No

Question 9

WIthout air resistance, if you toss a ball straight up and it falls straight down, is the time it takes to rise equal to the time it takes to fall?

Answer 9

Yeah

Question 10

What is an example of something having a constant speed but variable velocity?

Answer 10

Running in a circle at constant speed

Question 11

Can a component vector have a greater magnitude than the vector’s magnitude?

Answer 11

Nope

Question 12

A skier jumps off a ramp. How does air resistance affect him?

Answer 12

Air resistance opposes motion, so it slows down the object and reduces the range

Question 13

What is a projectile?

Answer 13

A projectile is an object that is thrown or launched into the air and moves under the influence of gravity and air resistance

Question 14

An object travelling east experiences an acceleration directed north, what is its direction some time later?

Answer 14

North-East

Question 15

True or False: Centripetal force can never be the result of static friction force

Answer 15

False, it CAN!

Question 16

When an object is travelling in uniform circular motion, what direction is the force?

Answer 16

Radially Inward

Question 17

For an object in uniform circular motion, what direction is the instantaneous velocity?

Answer 17

tangent to the circle

Question 18

Which particle experiences the largest centripetal force in a centrifuge? A) r=5cm, m=0.1g, B)r = 2cm, m=0.1g C) r=2cm, m =0.05g
D)r = 5cm, m = 0.05g

Answer 18

b)

Question 19

An object in uniform circular motion with speed v experiences a centripetal force of, Fc. What value of Fc is needed if the radius of the path is halved and velocity is halved?

Answer 19

Fc / 2

Question 20

A 1.5-kg cart is pulled with a force of 7.3 N at an angle of 40° above the horizontal. If a kinetic friction force of 3.2 N acts against the motion, the cart’s acceleration along the horizontal surface will be

Answer 20

1.6 m/s^2

Question 21

A child with mass m is sliding down a slide that is inclined at an angle of q above the horizontal. The magnitude of the normal force on the child is:

Answer 21

mgcosq

Question 22

Big Bubba has a mass of 100 kg on the earth. What is Big Bubba’s mass on the moon where the force of gravity is approximately 1/6-th that of Earth’s? ________ Explain or show your work.

Answer 22

100kg

Question 23

What is centrifugal force?

Answer 23

the centrifugal force is what’s known as a fictitious force: It’s an apparent outward force on an object that is moving in a circle. This phantom force can nevertheless feel very real if you are the one rotating

Question 24

Can three vector forces add up to zero?

Answer 24

Yes

Question 25

A car undergoes uniform circular motion on a banked curve. What is providing the centripetal force?

Answer 25

When the curve is banked, the centripetal force can be supplied by the horizontal component of the normal force. In fact, for every banked curve, there is one speed at which the entire centripetal force is supplied by the horizontal component of the normal force, and no friction is required.

Question 26

Is centripetal force a fundamental force of nature?

Answer 26

NAh

Question 27

A drink is resting on a table. If the earth's force of gravity on the can is the action force, what is the reaction force?

Answer 27

The force exerted by the can on the earth

Question 28

A child whirls a ball around in circles on the end of a 48 cm long string at a frequency of 2.5 Hz. What is the ball’s centripetal acceleration?

Answer 28

1.2 x 102 m/s2

Question 29

You are whirling a rubber stopper attached to a string in a vertical circle. When you reduce the speed so that the stopper barely makes it over the top of the circle, at the highest point, what is the net force? (Direction + relation to mg)

Answer 29

The net force would be vertical and equal in magnitude to mg.

Question 30

A skier of mass m is sliding down a snowy slope that is inclined at an angle φ above the horizontal. The magnitude of the normal force on the skier is: (a) mg tan φ (b) mg cos φ (c) mg sin φ (d) mg (e) zero

Answer 30

B

Question 31

A car goes over a hill, when does the car achieve its fastest speed possible whilst still being in uniform circular motion?

Answer 31

The car achieves its fastest speed if there is no normal force at the top of the hill

Question 32

What provides the centripetal force when a car moves in uniform circular motion around a flat circular track?

Answer 32

Static Friction

Question 33

When do you feel the heaviest when you go through a Loop-the-Loop in a roller coaster?

Answer 33

At the very bottom because the normal force is at its largest

Question 34

If you stand on a spinning disk, undergoing uniform circular motion, what is providing the centripetal force?

Answer 34

Force of Friction