physics

a 6.0*10^-2 kg tennis ball moves at a velocity of 12m/s. the ball is struck by a racket, causing it to rebound in the opposite direction at a speed of 18m/s. what is the change in the ball's momentum?

-1.8 m/s- JUST MAKE THE SECOND VELOCITY NEGATIVE

an astronaut with a mass of 85 kg is outside a space capsule when the tether line breaks. to return to the capsule, the astronaut throws a 2 kg wrench away from the capsule at a speed of 14m/s. at what speed doesn't the astronaut moves towards the capsule?

0.33 m/s

A worker does 25 J of work lifting a bucket, then sets the bucket back down in the same place. What is the total net work done on the bucket?

0J

a child moving at a constant velocity carries a 2 N ice cream cone 1m across a level surface. what is the net work done on the ice cream cone?

0J

write an equation that expresses the conservation of mechanical energy in a system that involves KE, PEg, and elastic PE.

1/2mvi^2+ mghi + 1/2 kxi^2 = 1/2 mvf^2 + mghf + 1/2 kxf^2

what is the kinetic energy of a 0.135 kg baseball thrown at 40m/s?

108J

Which motor performs more work in the same amount of time—a 10 kW motor or a 20 kW motor? How much more work can it do?

20kW motor, 2x as much

If both the mass and the velocity of a ball are tripled, the kinetic energy of the ball is increased by a factor of

27

old faithful geyser shoots water every hour to a height of 40m. with what velocity does the water leave he ground?

28 m/s

a 3kg toy falls from a height of 1m. what will the KE of the toy be just before it hits the ground?

29.4 J

a professional skier starts from rest and reaches a speed of 56 m/s on a ski slope angled 30 degrees above the horizontal. using the work- KE theorem and disregarding friction, find the minimum distance along the slope the skier would have to travel in order to reach this speed?

320 M

a worker pushes a box with a horizontal force of 50 N over a level distance of 5m. if a frictional force of 43 N acts on the box in a direction opposite to that of the worker, what net work is done on the box?

35 J

KE of a car weighing 1.5*10^3 kg traveling at 25 m/s

4.7*10^5

what's the average power supplied by a 60kg person running up a flight of stairs a vertical distance of 4m in 4.2s?

560 W

what is the potential energy of a 1kg mass 1m above the ground?

9.81 J

a 0.2kg baseball is pitched with a velocity of 40m/s and is then batted to the pitcher with a velocity of 60m/s. what is the magnitude of change in the ball's momentum? a. 2 b. 4 c. 8 d. 20

B. 4

which of the following parameters does NOT depend on how resistant a spring is to being compressed or stretched? a. compression distance b. relaxed length c. spring constant d. stretching distance

B. relaxed length

Law of Conservation of Mechanical Energy

ENERGY CAN'T DISAPPEAR. The total amount of mechanical energy, in a closed system in the absence of dissipative forces (e.g. friction, air resistance), remains constant. This means that potential energy can become kinetic energy, or vice versa, but energy cannot "disappear".

why doesn't the principle of mechanical energy conservation golf in situations when frictional forces are present?

KE is not completely converted to a form of PE

inelastic collision

KE isn't conserved

what form of energy is associated with the position of an object in earth's gravitational field?

PEg

which of the following statements properly relates the variables in the equation F🔺t=🔺p?

a large constant force acting over a long time interval causes a large change in momentum (just remember, long, long, long)

which of the following statements about the conservation of momentum is NOT correct? a. momentum is conserved for a system of objects pushing away from each other. b. momentum is not conserved for a system of objects in a head-on collision. c. momentum is conserved when two or more interacting objects push away from each other. d. the total momentum of a system of interacting objects remains constant regardless of forces between the objects.

b. momentum is not conserved for a system of objects in a head-on collision.

which of the following best describes the momentum of two bodies after a two-body collision if the kinetic energy of the system is conserved? a. must be less b. must also be conserved c. might also be conserved d. is doubled in value

b. must also be conserved

perfectly inelastic collision

collision in which kinetic energy is not conserved due to the action of internal friction. (KE isn't conserved, two bodies bonded)

for which of the following situations is the conservation of mechanical energy most likely to be a valid assumption? a. skateboard rolling across a sewer grate b. a parachutist falls from a plane c. rubbing your hands together to keep warm d. soccer ball flying through the air

d. soccer ball flying through the air

elastic collision

elastic collision is an encounter between two bodies in which the total kinetic energy of the two bodies after the encounter is equal to their total kinetic energy before the encounter

explain the scientific meaning of work

exerting force one object and moving it a distance

the equation for determining gravitational potential energy is PE=mgh. which factor in this equation is not intrinsic in an object?

g and h

If friction is the only force acting on an object during a given physical process, which of the following assumptions can be made in regard to the object's kinetic energy?

kinetic energy decreases

perfectly elastic collision

no loss of kinetic energy in the collision.

is it possible for a spaceship traveling with constant velocity to experience a change in momentum? explain

no, because the velocity isn't changing and the mass won't. p=mv

show how the alternative definition of power can be derived by substituting the definitions of work and speed into the standard definition of power, p=w/t

p= w/t= fd/t = mgd / t

Two balls of dough collide and stick together. Identify the type of collision.

perfectly inelastic

EXTRA STUFF TO REMEMBER

sohcahtoa for height after pe=ke KE=PE mv=mv when momentum is conserved S AND W AND OPPOSITE/ SECOND VELOCITY MEAN NEGATIVE p first, then p=ft, then d=(vi+vf)/2 (t) for t and x

a train with a mass of 1.8*10^-3 kg is moving at 15 m/s when the engineer applies the breaks. if the braking force is constant at 3.5*10^4 N, how long does it take the train to stop? how far does the train travel during this time?

t=77s, x=580m

If the sign of work is negative,

the displacement is in the direction opposite the force

Two objects with different masses collide and bounce back after an elastic collision. Before the collision, the two objects were moving at velocities equal in magnitude but opposite in direction. After the collision,

the more massive object had gained momentum

Two swimmers relax close together on air mattresses in a pool. One swimmer's mass is 48 kg, and the other's mass is 55 kg. If the swimmers push away from each other,

their momenta are equal but opposite