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QveST [7]
3 years ago
14

A small boat coasts at constant speed under a bridge. A heavy sack of sand is dropped from the bridge onto the boat. The speed o

f the boat
a. does not change.
b. increases.
c. Without knowing the mass of the boat and the sand, we can't tell.
d. decreases
Physics
1 answer:
Tju [1.3M]3 years ago
7 0

Answer:

d. decreases

Explanation:

The law of conservation of momentum tells us that the sum of momenta before the collision is equal to the sum of momenta after the collision. The bag has no momentum as it falls onto the boat because its velocity is zero in the horizontal direction. But after it hits the boat, it's momentum increases while the momentum of the system remains the same. That means a component of the system must decrease somewhere else. And that component is the velocity, not the mass, of the boat.

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A 2000 kg roller coaster is at the top of a loop with a radius of 24 m. If its speed is 18 m/s at this point, what force does it
levacccp [35]

Answer:

46620\ \text{N}

Explanation:

m = Mass of roller coaster = 2000 kg

r = Radius of loop = 24 m

v = Velocity of roller coaster = 18 m/s

g = Acceleration due to gravity = 9.81\ \text{m/s}^2

Normal force at the point will be

N-mg=\dfrac{mv^2}{r}\\\Rightarrow N=\dfrac{mv^2}{r}+mg\\\Rightarrow N=\dfrac{2000\times 18^2}{24}+2000\times 9.81\\\Rightarrow N=46620\ \text{N}

The force exerted on the track is 46620\ \text{N}.

8 0
3 years ago
A flare is launched from a life raft with an initial velocity of 192 ft/sec. How many seconds will it take for the flare to retu
DIA [1.3K]

We use the formula,

h= ut- 16 t^2

Here, h is the  variable  represents the height of the flare  in feet when it returns to the sea so, h = 0 and u is the initial velocity of the flare, in feet per second and its value of 192 ft/sec.

Substituting these values in above equation, we get

0 = 192 t - 16 t^2  \\\\ 16 t( 12 - t ) =0 \\\\ t = 12 s.

Here, t= 0 neglect because it is  the time when the flare is launched.

Thus, flare return to the sea in 12 s.

8 0
3 years ago
What can alter the motion of an object
Liula [17]
Force can alter its direction,slow or stop it you could say it can change its velocity

3 0
3 years ago
A real battery with internal resistance 0.460 Ω and emf 9.00 V is used to charge a 56.0-µF capacitor. A 21.0-Ω resistor is put i
Margaret [11]

Answer: 1.176×10^-3 s

Explanation: The time constant formulae for an RC circuit is given below as

t =RC

Where t = time constant , R = magnitude of resistance = 21 ohms , C = capacitance of capacitor = 56 uf = 56×10^-6 F

t = 56×10^-6 × 21

t = 1176×10^-6

t = 1.176×10^-3 s

4 0
3 years ago
Read 2 more answers
If an exit sign is hanging from the ceiling by three chains each of which has a tension of 15N what is the weight of the sign
kvasek [131]
The weight is 45 N, because the three chains hold the sign, and each contributes 15 N.

Notice that the mass would be the weight/acceleration of gravity, m = 45/9.8 kg. But they ask the weight (force, so Newtons)
3 0
3 years ago
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