Monday
December 22, 2014

Homework Help: Physical Science

Posted by Toni on Sunday, January 2, 2011 at 10:03pm.

I have a really good grade in this class and I need to keep it that way. I am only asking to have my answers checked. I would like to graduate with honors so please help if you can.

1. A car traveling along the highway needs a certain amount of force exerted on it to stop. More stopping force may be required when the car has:
My choice is D
A. more momentum
B. less stopping distance
C. more mass
D. all of the above

2. Padded dashboards in cars are safer in an accident than non-padded ones because an occupant hitting the dashboard has: my choice is c
A. decreased impact force and decreased impulse
B. decreased impact force and increased time of impact
C. increased time of impact and decreased impulse
D. increased time of impact and increased impulse

3. If a cannonball is shot from a longer barrel cannon rather than a shorter barrel cannon, it will have a: choice is d
A. smaller speed leaving the longer barrel because of smaller impulse
B. larger speed leaving the longer barrel because of larger impulse
C. smaller speed leaving the longer barrel because it received a less steady force.
D. larger speed leaving the barrel because it received a more steady force

4. Two balls having the same mass of 1 kg roll toward each other, each moving at the same speed of 1 m/s. What is the combined momentum of the two balls?
My choice is A
A. 0 kg
B. 0.5 kg
C. 1 kg
D. 2 kg

5. A 5 kg fish swimming at a speed of 1 m/s swallows an abset-minded 1 kg fish swimming toward it at 4 m/s. The speed of the larger fish after lunch is ____ m/s. I choose A
A. 1/6
B. 1/2
C. 2/3
D. 3/2

6. A 30 kg girl and a 25 kg boy face each other on friction-free roller blades. The girl pushes the boy, who moves away at a speed of 1.0 m/s. The girl's speed is ____ m/s. My answer is C
A. 0.45
B. 0.55
C. 0.83
D. 1.2

7. A 1000 kg car moving at 10 m/s brakes to a stop in 5 s. The average braking force is ___N. My answer B
A. 1000
B. 2000
C. 4000
D. 5000

8. Two identical freight cars roll without friction towards each other on a level track. One rolls at 2 m/s and the other rolls at 1 m/s. After the cars collide, they couple and roll together with a speed of ____ m/s. My answer is B
A. 0.33
B. 0.5
C. 0.67
D. 1.0

9. The power expended when a 10n barbell is raised 2.0 m in 2 s is ____ watts. Mine is C
A. 0.4
B. 2.5
C. 10
C. 40

10. A TV set is pushed a distance of 2 m with a force of 20 n that is in the same direction as the set moves. How much work is done on the set? Mine is C
A. 10j
B. 20j
C. 40j
D. 80j

11. A 20 kg mass is held 4m abouve the ground. What is the approximate potential energy of the mass with respect to the ground? Mine is D
A. 5j
B. 50j
C. 80j
D. 800j

12. A car moves 4 times as fast as another identical car. Compared to the slower car, the faster car has ____ times the KE. Mine is d
A. 2
B. 4
C. 8
D. 16

13. A machine puts out 100w of power for every 1000w put into it. The efficiency of the machine is: mine a
A. 10%
B. 50%
C. 90%
D. 110%

14. Car a travels four times as fast as car b. When braking to a stop, car a skids ____ times as far as car b. mine is d
A. 0.25
B. 0.5
C. 4
D. 16

15. No work is done by gravity on a bowling ball that is rolled along a bowling alley because: mine is D
A. no distance is covered by the ball
B. no force acts on the ball
C. no potential energy is being coverted to kinetic energy
D. the force on the ball is at right angles to the ball's motion

16. When a bullet is fired from a rifle: mine is D
A. the recoiling rifle and the bullet have the same kinetic energy and momentum
B. the bullet has greater momentum and kinetic energy than the rifle
C. the rifle has greater momentum and kinetic energy than the bullet
D. they have the same momentum, but the bullet has greater kinetic energy than the rifle

17. If earth's mass decreased to one-half its original mass with no change in radius, then your weight would: mine is B
A. stay the same
B. decrease to 1/2 your original weight
C. decrease to one-quarter your original weight
D. double your original weight

18. When the distance between two stars decreases by half, the force between them: mine is a
A. increases to four timees as much
B. increases to twice as much
C. decreases to 1/2
D. decreases by one-quarter

19. Two objects move towards each other because of gravity. As the objects get closer and closer, the acceleration of each: mine is B
A. decreases because the force decreases
B. stasy the same because the force stays the same
C. increases due to increased force between them
D. decreases due to increased momentum in opposite directions.

20. During an eclipse of the sun (when earth, moon, and sun are lined up), the ocean tides on earth are extra ____ and are called ____ tides. Mine is B
A. low, spring
B. high, spring
C. low, neap
D. high, neap

21. A projectile shot straight forward at the edge of a cliff will: mine C
A. have constant motion vertically and accelerated motion horizontally
B. follow a curved path called an ellipse
C. hit the ground at the same time as a dropped stone
D. not be slowed by air drag because it is moving so fast

22. A ball is thrown upwards and caught when it comes back down. Neglecting air-resistance, which statement is true? mine A
A. Its speed is the same as it had when thrown upwards and the time going up equals the time coming back down
B. Its speed is less than when it was thrown upwards and the time going up is greater than the time coming down
C. its speed is more than when it was thrown upwards and the time going up is less than the time coming down
D. its speed is the same as when it was thrown upwards and the time going up is greater than the time coming back down.

23. A projectile is thrown into the air at an angle of 35 degrees and lands on a target that is at the same level the projectile started. it will also lang on the target if it is thrown at an angle of: mine c
A. 15
B. 25
C. 55
D. 65

24. When a rock thrown straight upwards gets to the exact top of its path, its velocity is: mine D
A. 0 and its acceleration is 0
B. about 10 m/s and its acceleration is 0
C. about 10 m/s and its acceleration is about 10 m/s/s
D. 0 and its acceleration is about 10 m/s/s

25. The fastest moving planet in a solar system is: mine C
A. the smallest planet
B. any planet, because they all move at the same speed
C. the planet nearest the sun
D. the planet farthest from the sun

Thank you for checking my answers for me.

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