Answer:
a. −0.12m/s
Explanation:
Given;
mass of the hockey goalie, m₁ = 65 kg
mass of the hockey puck, m₂ = 0.15 kg
velocity of the hockey puck, u₂ = 50 m/s
initial velocity of the hockey goalie, u₁ = 0
let the recoil velocity of the goalie = v
Apply Newton's third law of motion;
action and reaction are equal and opposite.
m₁v = -m₂u₂
65v = -(0.15 x 50)
65v = -7.5
v = - 7.5 / 65
v = -0.12 m/s
This shows that the goalie will move backwards with a velocity of 0.12 m/s.
Answer:

Explanation:
As we know that initial speed of the crate is


now finally the crate will come to rest
so we have

now the deceleration due to frictional force is given as

distance moved by the crate before it will stop is given as

so we will have


Answer:
= 8.5264
Explanation: Power is the rate of energy transferred per unit of time: P = 
The energy from the engine is converted into kinetic energy, which is calculated as: 
To compare the power of the two cars, first find the Kinetic Energy each one has:
<u>K.E. for Model A</u>

<u>K.E. for model B</u>


Now, determine Power for each model:
<u>Power for model A</u>
= 
<u>Power for model B</u>

Comparing power of model B to power of model A:

8.5264
Comparing power for each model, power for model B is 8.5264 better than model A.
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Answer:
Q (heat) = S * m * (T2 - T1) where Q is heat gained (loss), S the specific heat capacity of the substance and T2, T1 are the final and initial temps
Q = .215 cal / (g deg C) * 5 g * (20 - 80) deg C = -64.5 cal
Since the question specifies the heat emitted, then 64.5 cal is the
heat emitted (loss).
Explanation:
It is said that the bus moves with the speed of 72 km/hr.
It means that the bus covers 72 km in 1 hour.
so,
It covers 72 * 1000 m = 72000 m in one hour.
Hope it helps :)