Work, Energy And Momentum Flashcards
When a force moves an object, what is transferred and what is done?
Energy is transferred
And work is done
What’s the unit for work and energy
Joule(J)
What’s the equation for the work done? Give units
W(J) = F(N) x d(m)
What happens if the distance moved is zero?
No work is done on the object.
What does energy transferred equal?
Work done
What is the work done on an object if a force of 300 N movies it a distance of 8m?
2400J
The GPE of an object depends on what?
On it’s weight and how far it moves vertically
How can the change in GPE be calculated ?
Ep= mxgxh
What is the increase in Ep when a mass of 40kg is lifted 8m vertically?
320J
What is power?
The rate of transfer of energy
How can power be calculated?
P(W) = E(J) /t(s)
The kinetic energy of a moving object depends on?
It’s mass and speed
How can kinetic energy be calculated?
E(J) = 1/2 x m x v2
A boy of mass 40kg runs at a speed of 5m/s. What is his kinetic energy?
500J
When a spring is squashed and release it warms up. Why?
Some elastic potential energy is transferred by heating.
What happens if an elastic band is stretched and released?
Elastic potential energy is transferred to kinetic energy.
What do all moving objects have?
Momentum
The greater the mass and the greater the velocity of an object, the greater it’s ….?
Momentum
When do objects have momentum
When they’re moving
How can momentum be calculated give units.
p(kgm/s) = m x v
What’s the momentum of a 1000 kg car travelling at 30m/s?
30,000 kgm/s
What does the conservation of momentum state?
When objects collide the total momentum before is equal to the total momentum after.
Two students on roller skates stand holding each other in the playground. They push each other away. What can you say about the momentum of each student?
It is equal and opposite
When two objects push each other apart, they move apart :?
With different speeds- if they have unequal masses
Equal and opposite momentum so their momentum is zero
