A
Name the applied force that moves a car forward
Thrust
A ball has a mass of 1 kg and accelerates at a rate of 3 m/s^2. Find the Net Force acting on the ball.
Fnet = 3 N
If you push a wall with a Force F=15 N , from left to the right, tell magnitude and direction of the reaction.
Magnitude = 15 N
Direction: from right to the left (to you)
What is Momentum? (concept and formula)
The ability to move bodies
p=m*v (mass*velocity)
What is Impulse?
The change in Momentum of a body.
An object is moving at a constant velocity.
What is the name of the system of forces affecting this object?
Balanced
A car has a mass of 1200 kg. The resultant (net) force acting on the car is 3600 N in the forward direction.
Calculate the acceleration of the car.
3 m/s^2
Tell the formula of the Force of gravity (or Weight)
Fg = Weight = m*g (mass*acceleration of gravity)
Is momentum a scalar or a vector quantity?
Is its direction the same or opposite to velocity?
Vector quantity
Same direction as velocity
What are the two SI units for impulse?
kg*m/s
N*s
A person falling form an airplane (in free fall), who has NOT reached the terminal velocity yet, is affected by a balanced or unbalanced system of forces?
Unbalanced
A 5.0 kg trolley is initially travelling at 4.0 m/s. A Net Force of 15 N acts on the trolley in the direction of motion for 6.0 s.
a) Calculate the acceleration of the trolley.
b) Calculate the final velocity of the trolley.
a= 3 m/s^2
Vf = 22 m/s
A swimmer pushes the water backwards with their hands. According to Newton’s Third Law, why does the swimmer move forwards?
The water exerts an equal and opposite force on the swimmer, pushing them forwards.
Is Momentum conserved in an isolated or non-isolated system?
Momentum is conserved in an isolated system
A tennis ball of mass 0.060 kg is thrown horizontally towards a wall at 3.0 m/s. The ball bounces back from the wall at 2.0 m/s.
Calculate the impulse on the ball.
J = 0.3 kg*m/s (or N*s) = magnitude only
(the sign of J will depend on the direction chosen as positive).
What is Inertia?
The resistance to the change in the status of motion.
A 900 kg car is slowing down because a Net Force of ...3600 N acts opposite to its direction of motion. The force acts for 6.0 s, and the car's final velocity is 10 m/s.
a) Calculate the acceleration of the car.
b) Calculate the initial velocity of the car.
a=-4 m/s^2
vi = 34 m/s
An apple falls on the ground. Why do you only see the apple moving and not the Earth moving toward the apple?
An apple falls to the ground. Why do we see the apple moving but not the Earth moving towards the apple?
Two identical trolleys, each with a mass of 2.0 kg, collide on a horizontal track. Before the collision, trolley A is moving to the right at 6.0 m/s, while trolley B is at rest. After the collision, trolley A stops. The system is isolated.
Calculate the magnitude and direction of trolley B after the collision.
vB = 6 m/s to the right (after collision)
A car of mass 1200 kg is travelling at 10 m/s to the right. The car receives a further impulse of 6000 kg*m/s to the right.
Calculate the final velocity of the car.
vf = 15 m/s, to the right
A car is decelerating (or retarding).
Is the direction of the Net Force the same as the direction of motion or opposite to it?
opposite to the direction of motion
A 1000 kg car is travelling along a straight, horizontal road. The engine provides a forward driving force of 5000 N. The car accelerates from 10 m/s to 18 m/s in 4.0 s.The car experiences a resistance force due to friction and air resistance acting opposite to its motion. Calculate the total resistance force acting on the car.
Resistance force = 3000 N
According to Newton’s Third Law, if you push a wall, the wall pushes back with an equal and opposite force. Why does the wall not move, while an aeroplane can move forward by pushing air backwards?
The wall is fixed to the ground, which provides a reaction force that prevents it from accelerating. An aeroplane, however, pushes air backwards; the air pushes the aeroplane forwards with an equal and opposite force, allowing it to accelerate.
A rocket and its fuel have a total mass of 1200 kg and are travelling at 50 m/s to the right. The rocket ejects 200 kg of gas backwards at 20 m/s to the left.
Assume there are no external forces acting on the rocket during the ejection.
Calculate the final velocity of the rocket after the gas has been ejected.
Vf (rocket) = 64 m/s, to the right
A tennis ball of mass 0.060 kg is moving at 8.0 m/s to the left. A racket hits the ball, causing it to move at 12.0 m/s to the right. The average net force acting on the ball is 60 N to the right.
Calculate the time for which the racket is in contact with the ball.
t=0.02 s