Heater supplies 80 J of energy to a block of metal. The temperature of the block rises by 20 °C. What happens to the block of metal when its temperature falls by 10°C?
Its internal energy increases by 40 J.
Its internal energy decreases by 40 J.
Its internal energy decreases by 160 J.
Its internal energy increases by 160 J.

Its internal energy decreases by 40 J.

Explanation:

The energy supplied to the metal block causes the temperature of the block to rise. Therefore,

Now, we will use this value of mC to find out the energy change of block:

It shows that when the temperature of the metal block falls by 10°C,

Its internal energy decreases by 40 J.

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s

the answer is 12 as i may remember

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