Exam 2

As a diver falls towards a water's surface, what happens to the diver's KE and PE ?

KE increases and PE decreases

A ball of mass M=0.6 Kg is tossed vertically upward from a flat ground with initial Kinetic Energy= 750 J. There is no air resistance. At time t= 3 seconds, the potential energy of the ball is _______ J

630

A ball kicked with a velocity Vo moves in a parabola and covers a range R on Earth. If the same ball is kicked with the same velocity on the Moon, it covers_______

more range

As a ball falls down without air resistance, the momentum of the ball ______________

increases

In which of the following situations is the greatest power exerted ?

10 J of work done in 0.5 s

A big fish with mass M1= 40 Kg swims to the right at V1i= 3 m/s. A small fish of mass M2= 8 Kg swims in the opposite direction to the left. The two fish then make a collision; the bigger fish swallows the smaller fish and both stop finally (Vf=0). The velocity V2i of the smaller fish before collision is negative ______ m/s

15

Starting at rest (W0=0), a fan makes uniform angular acceleration and acquires a final rotational velocity Wf= 600 RPM in time t=5 minutes. The number of rotations (N) the fan makes in 5 minutes is ____ rotations

1500

A toy spring gun has spring constant K= 800 N/m. A ball of mass M= 0.5 Kg is in contact with the spring. The ball is pushed until the spring is compressed by delta X= 0.4 m. The system is friction less. The velocity of the ball as it comes out of the gun= V ball=________ m/s.

16

An air plane flies horizontally with a velocity V0X= 480 m/s. A package having mass M= 20 Kg falls off the plane. The plane was flying at an altitude H=Dy= 6480 m above ground. V0Y=0. The horizontal distance Dx (range) the package travels before striking the ground is _______ meters.

17, 280

A diver of mass M = 52 Kg stands at rest on a diving board at a height H=D= 45 m above the water's surface. There is no air resistance. Take g= 10 m/s2. The final kinetic energy of the diver just before entering the water is ____ Joules

23, 400

A pendulum of length L=6 m oscillates back and forth with Period T= 3.08 s on a planet with an unknown value of acceleration due to gravity (g). The acceleration due to gravity on the planet is g =______ m/s2.

25

A car having mass M = 1800 Kg moves around a flat circular road of radius R= 90 m. The maximum amount of friction available between the tire and the road = F= 15, 680 N. The maximum speed the car can have without getting out of the curve is Vmax = ________ m/s

28

A bullet of mass M1= 0.4 Kg moving initially at V1i= 1000 m/s strikes and gets embedded into a wooden block of mass M2= 3.6 Kg that was initially at rest (V2i=0) on a horizontal friction less surface. After impact, the bullet-block combination compresses a spring of spring constant K = 1600 N/m. The maximum amount (delta X ) by which the spring gets compressed is delta X = _______ m

5

A person having mass M= 70 Kg stands at rest on a diving board at a height H= 45 m above the water's surface. The initial potential energy of the person is ______ Joules.

31, 500

A box of mass M= 40 Kg was initially at rest. The box accelerates at a= 5 m/s2 for a time t= 8 seconds. The work done on the box is_____ Joules.

32,000

A car having mass M1= 1000 Kg moving initially at V1i= 80 m/s makes a collision with a car of mass M2= 4000 Kg moving with an initial velocity V2i=20 m/s. After collision, the two cars stick and move together._____ % of the KE of the cars is lost in the collision.

36

A spring has spring constant K= 600 N/m. If the spring is compressed by delta X= 0.40 m, the potential energy stored in the spring is ________ J

48

A box of unknown mass, which was initially at rest , is pushed by a net force F net = 200 N. After it is pushed for time t= 8 seconds, its final velocity is Vf= 32 m/s. The mass of the box is M =_______ Kg

50

Starting at rest (W0=0), a motor makes uniform angular acceleration and acquires a final rotational velocity Wf= 4000 RPM in a time t=8 minutes. The motor's angular acceleration is________ RPM/min

500

A car of mass M =2000 Kg moves with kinetic energy = 784, 000 J. The momentum of the car is P=_____ Kg.m/s

56, 000

A bullet of mass M= 0.02 Kg moves with a velocity V= 800 m/s. The kinetic energy of the bullet is _______ Joules.

6400

Three children sit on opposite sides of a uniform seesaw which pivots at the center. Child A has mass 80 Kg and sits 5 m from the center to the left of the fulcrum. Child B and child C sit to the right of the fulcrum.Child B has a mass of 60 Kg and sits 4 m to the right of the fulcrum. Child C has a mass of 20 Kg. Child C must sit _____ m to the right of the fulcrum for the seesaw to balance.

8

An air plane flies horizontally with a velocity VOX= 640 m/s while a package of mass M= 40 Kg falls off from the plane. The plane was flying at an altitude=H=Dy= 11, 520 m above ground. There is no air resistance, and VOY=0. The final total velocity of the package just before it hits the ground is ______ m/s, SE.

800

If a box is pushed by a horizontal force F= 200 N and the box moves through a distance d= 40 m in the direction of the force, the work done by the force on the box is _____ Joules.

8000

A rope is attached to a box of mass M= 60 Kg. The box is accelerated upward with a=5m/s2. The tension force exerted by the rope on the box is ______ N

900

A car of mass M1= 1000 Kg moving initially at an UNKNOWN velocity (V1i=?) strikes a car of mass M2= 3000 Kg which was initially at rest (V2i=0). After impact, the two cars stick together and slide through a distance d= 36 m (length of skid mark) until they finally stop. While they slide together, the net frictional force exerted on the coupled cars is NEGATIVE 32, 000 N. The initial velocity of the 1000 Kg car before the collision is V1i=______ m/s.

96

If a ball of mass M is rotating at the same speed V on a circle of radius R, then its acceleration is zero.

False

When a big car hits a small car, the collision force exerted by the bigger car on the smaller car is larger than the collision force exerted by the smaller car on the bigger car.

False

A ball of mass M kicked from the ground moves in a parabolic path. At the highest(top) point of the parabola, the ball's_______________

PE is maximum

When an ice skater pulls her arms inward, her rotational speed increases since her rotational inertia_______

decrease

If lever arm is doubled, the torque exerted by a given force _______

doubles

A pendulum swings repeatedly back-and-forth from extreme left-to-center-to extreme right-to center-to extreme left, etc. The potential energy of the pendulum is greatest at_______ position

extreme left and extreme right

As a ball moves in a parabola without air resistance, its ______ velocity remains the same.

horizontal

If a car doubles its velocity, the car's kinetic energy __________.

quadruples

RPM (rotations per minute) is a unit of ________

rotational velocity

Child A sits at the edge (end) of a rotating merry go round, while child B sits mid way between the center and the edge of the merry go round. This means child A is twice as far away from the center as child B. Then, child A and child B have______

same rotational speed but different tangential speeds

In order to stop a fast moving car, it is better to hit a hay stack than a cement wall since the hay stack exerts _____

smaller force in more time

A hollow disk and a solid disk have the same mass and radius. Starting at rest, both roll down simultaneously down an inclined surface. The _____ disk reaches the bottom first.

solid

A mass M oscillates up-and-down while attached to a spring having spring constant K. If the mass becomes 9 times bigger, the period (T) of oscillation ___________

triples

You exert torque when you__________

use a wrench, open a door and turn a steering wheel