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3 years ago

The mass of an object with 500 J of kinetic energy moving with a velocity of 5 m/s is

Physics

1 answer:

Ann [662]3 years ago

4 0

40kg

Explanation:

Given parameters:

Kinetic energy = 500J

Velocity = 5m/s

Unknown:

Mass of the object = ?

Solution:

Kinetic energy is the energy due to motion of a body. It is expressed as:

K.E = $\frac{1}{2}$ mv²

m is the mass of the body

v is the velocity

To find the mass, make it the subject of the expression:

m = $\frac{2 K.E}{v[tex]^{2}$ }[/tex]

m = $\frac{2 x 500}{5[tex]^{2}$ }[/tex] = 40kg

Learn more:

Kinetic energy brainly.com/question/6536722

#learnwithBrainly

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A hockey puck on a frozen pond is given an initial speed of 20.0 m/s. If the puck always remains on the ice and slides 115 m bef

bekas [8.4K]

Answer:

μ_k = 0.1773

Explanation:

We are given;

Initial velocity;u = 20 m/s

Final velocity;v = 0 m/s (since it comes to rest)

Distance before coming to rest;s = 115 m

Let's find the acceleration using Newton's second law of motion;

v² = u² + 2as

Making a the subject, we have;

a = (v² - u²)/2s

Plugging relevant values;

a = (0² - 20²)/(2 × 115)

a = -400/230

a = -1.739 m/s²

From the question, the only force acting on the puck in the x direction is the force of friction. Since friction always opposes motion, we see that:

F_k = −ma - - - (1)

We also know that F_k is defined by;

F_k = μ_k•N

Where;

μ_k is coefficient of kinetic friction

N is normal force which is (mg)

Since gravity acts in the negative direction, the normal force will be positive.

Thus;

F_k = μ_k•mg - - - (2)

where g is acceleration due to gravity.

Thus,equating equation 1 and 2,we have;

−ma = μ_k•mg

m will cancel out to give;

-a = μ_k•g

μ_k = -a/g

g has a constant value of 9.81 m/s², so;

μ_k = - (-1.739/9.81)

μ_k = 0.1773

3 0

3 years ago

If for every action force an equal and opposite reaction force exists, how can anything ever be accelerated?

sweet [91]

If there are two equal and opposite forces on the SAME THING, then the thing doesn't accelerate. You're right about that. But the action and reaction forces act on two different things. The bullet and the rifle. The ball and the bat. The airplane and the air. etc. So BOTH can accelerate.

8 0

3 years ago

find the time taken, if the speed of a train increased from 72 km/hr to 90 km/hr for 234 km. leave your answer in seconds

Airida [17]

Answer:

Time taken = 10400 s

Explanation:

Given:

Initial speed of the train, $u=72\textrm{ km/h}=72\times \frac{5}{18}=20\textrm{ m/s}$