Part 1 /3 High School by SSL Technologies Physics Ex-36 Click Kinetic energy is energy of motion. The faster an object is moving, the more kinetic energy.

Part 1 /3

High School

by SSL Technologies

Physics Ex-36

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Kinetic energy is energy of motion. The faster an object is moving,

the more kinetic energy it possesses. This is because the energy

required to increase the velocity of an object (the work done) goes

to the object in the form of kinetic energy.

The following formula is used to calculate the kinetic energy of an

object: EK = ½ mv2

where EK is the kinetic energy in joules (J) m is the mass of the object in kilograms (kg) v is the velocity of the object in m/sNote that the velocity is the velocity at any time (or instance)

and is known as the instantaneous velocity.

PART-1

Physics Ex-36

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When an object is accelerated, work is being done.

When an object is decelerated, the kinetic energy it has mustbe dissipated (reduced to zero).

When stopping a car, work is done by the brakes (friction) todissipate the energy. The EK of the car is transformed intoheat and sound.

The fact that the kinetic energy of an object is proportional to thesquare of its speed has important consequences. Doubling the speed of a car, for example, quadruples its kinetic energy (22).If the velocity increases ten times, then the EK becomes 100 timesgreater (102). This explains the highway slogan that “speed kills”.

PART-1

Physics Ex-36

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To find the work done to accelerate an object (energy used),find the change in the object’s kinetic energy as shown below:

Physics Ex-36Question-1

Is kinetic energy a scalar or a vector quantity?

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Kinetic energy is a scalar.

All forms of energyAll forms of energyare scalars.are scalars.

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In terms of basic units (L, M and T), what are the dimensionsof kinetic energy?

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The unit for energy is The unit for energy is kg kg mm22/s/s22 (or joules). (or joules).

REMEMBER

. It’s the Joule for any form of energy.

(Length, Mass and Time)


Where does the energy used to accelerate an object go?

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To the object in the form of KE (increased velocity).


A 20 kg object has a velocity of 10 m/s. What is its kinetic energy?

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Use g = 10 m/s2 for the Earth’s gravitational

acceleration.

Reminder


An object having a mass of 5 kg is traveling at 6 m/s.It accelerates to a velocity of 12 m/s. How much workwas done to accelerate the object?

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A 20 g bullet has a velocity of 25 000 cm/s. Calculate itskinetic energy.

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Convert grams to kilograms Convert cm/s to m/s

20 g = 0.02 kg 25 000 cm/s = 250 m/s


An object having a mass of 5 kg is dropped from a height of 20 m.How much kinetic energy does it have at the instant it strikes theground?

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A 2 kg object is thrown in the air with such a velocity that itskinetic energy is 25 J. How high does the object rise?

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Step-1: Find the initial velocity.

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Step-2: Find the time.

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Step-3: Find the height.


Object-A, of mass m, is moving with a velocity v.Object-B, of mass 2m, is moving with a velocity 2v.What is the value of the following ratio?

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Ek of object-A

EK of object-B


An 80 kg mass, moving with a velocity of 10 m/s, has its kineticenergy increased by 1.6 x 103 J.

What is the value of the final EK of the mass?

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A 1000 kg car is traveling at 10 m/s. If the brakes stop the carin 7 seconds, calculate the initial kinetic energy of the car.

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How much energy is required to get a 40 kg cart from restto a velocity of 25 m/s?

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How much energy is required to increase the velocity ofa 40 kg cart from 10 m/s to 30 m/s?

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Assuming that the coefficient of friction between the tiresand the road is 0.70, calculate the distance required tostop a 1500 kg car traveling at:

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a) 25 km/h


Assuming that the coefficient of friction between the tiresand the road is 0.70, calculate the distance required tostop a 1500 kg car traveling at:

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b) 50 km/h Convert km/h into m/s


What distance does a 20 g bullet traveling at 150 m/s penetrateinto a block of wood if the (average) force used to stop the bulletis 225 000 N?

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A 2 kg cart is traveling at 10 m/s on a horizontal surface towardssome sand. The sand decelerates the cart to a stop in a distanceof 5 m.

How much work did the sand do in stopping the cart? a)


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What was the (average) force exerted by the sand in stoppingthe cart?

b)


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What becomes of the kinetic energy of the cart? c)

It is lost to friction as heat and sound energy.


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A 2 kg cart is traveling at 10 m/s on a horizontal surface towardssome sand. After traversing the sandy area, a distance of 4 m,the velocity of the cart is 4 m/s

How much work did the sand do in slowing down the cart? a)

Negative sign indicates

cart lost energy.


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A 2 kg cart is traveling at 10 m/s on a horizontal surface towardssome sand. After traversing the sandy area, a distance of 4 m,the velocity of the cart is 4 m/s

What was the (average) force exerted by the sand in slowingdown the cart?

b)


Starting from rest, a 10 kg block of wood slides down a 30o inclineplane as shown in the diagram on the right. Determine its kineticenergy at a point 2.5 m from its starting position (along the plane).

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Part 1 /3 High School by SSL Technologies Physics Ex-36 Click Kinetic energy is energy of motion. The faster an object is moving, the more kinetic energy.

Documents

object energy

physics ex

ms slide

objectb slide

form of kinetic energy

initial kinetic energy

objects kinetic energy

dimensions of kinetic