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umka21 [38]
3 years ago
10

A woman on a bridge 82.2 m high sees a raft floating at a constant speed on the river below. She drops a stone from rest in an a

ttempt to hit the raft. The stone is released when the raft has 5.04 m more to travel before passing under the bridge. The stone hits the water 2.13 m in front of the raft. Find the speed of the raft.
Physics
1 answer:
solong [7]3 years ago
5 0

Answer:

0.71 m/s

Explanation:

We find the time it takes the stone to hit the water.

Using y = ut - 1/2gt² where y = height of bridge, u = initial speed of stone = 0 m/s, g = acceleration due to gravity = -9.8 m/s² (negative since it is directed downwards)and t = time it takes the stone to hit the water surface.

So, substituting the values of the variables into the equation, we have

y = ut - 1/2gt²

82.2 m = (0m/s)t - 1/2( -9.8 m/s²)t²

82.2 m = 0 + (4.9 m/s²)t²

82.2 m =  (4.9 m/s²)t²

t²  = 82.2 m/4.9 m/s²

t² = 16.78 s²

t = √16.78 s²

t = 4.1 s

This is also the time it takes the raft to move from 5.04 m before the bridge to 2.13 m before the bridge. So, the distance moved by the raft in time t = 4.1 s is 5.04 m - 2.13 m = 2.91 m.

Since speed = distance/time, the raft's speed v = 2.91 m/4.1 s = 0.71 m/s

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A person slaps her leg with her hand, which results in her hand coming to rest in a time interval of 2.75 ms2.75 ms from an init
kumpel [21]

Answer:

2677.3 N

Explanation:

v₀ = initial speed of the hand = 4.75 m/s

v  = final speed of the hand = 0 m/s

m = Total mass of hand and forearm = 1.55 kg

t = time interval for hand to come to rest = 2.75 ms = 0.00275 s

F = Force applied on the leg

Using Impulse-change in momentum equation

F t = m (v - v₀)

F (0.00275) = (1.55) (0 - 4.75)

F = - 2677.3 N

magnitude of force = 2677.3 N

6 0
3 years ago
Which scientist created the most modern classification that we use today
MrRissso [65]

Answer:

A. Aristotle

Explanation:

8 0
2 years ago
Read 2 more answers
1. A 9000 kg van was stopped at a traffic light when it rear-ended with an 850 compact car moving to the east at a velocity of 5
____ [38]

Answer:

1.785 m/s

Explanation:

The momentum can be calculated using the expression below

M1 *V1 + M2 * V2 = (M1+M2) V3

M1= mass of van=9000 kg

M2= mass of car= 850kg

V3= velocity of entangled car

V1= Velocity of the van= 0

V2= velocity of the car= 5 m/ s

Substitute the values

(900×0) + (500×5)=( 900+500)× V3

2500=1400 V3

V3=2500/1400

V3= 1.785 m/s

Hence, velocity of the entangled cars after collision is 1.785 m/s

8 0
2 years ago
Pls help me with this question
Arisa [49]

Answer:

dam 15 marks for that question that's ez marks there

4 0
2 years ago
The arrows in the chart below represent phase transitions.
Vikentia [17]

Answer:

1, 2, and 3.

Explanation:

Hello.

In this process, since the phase transitions that require energy are those that pass from a state with less energy or more molecular order to a state with more energy or less molecular order, say, from solid to liquid (melting), from liquid to gas (boiling) and from solid to gas (sublimation), we can conclude that the arrows representing heat energy gained are 1, 2, and 3 since 1 represents boiling, 2 melting and 3 sublimation.

Best regards.

6 0
2 years ago
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