Newton's second law Flashcards
What is inertial mass?
A measure of how difficult it is to change the velocity of a moving object.
It is defined as the ratio ‘force over acceleration’.
What happens when a resultant force acts on a mass, and what does it determine?
There will be a change in its velocity, and the resultant force determines the size and direction of the acceleration of the mass.
The acceleration will be in the same direction as the force.
A negative force means that the object is accelerating backwards or slowing down.
How do you calculate acceleration using the resultant force?
acceleration (m/s²) = force (N) ÷ mass (kg)
a = F ÷ m
Force:
F = m × a
What are the units for velocity?
m/s
What will the acceleration be if the resultant force is 0 N?
zero
What are the units for acceleration?
m/s²
What are the units for speed?
m/s
A basketball player catches a ball. The force acting on the ball is -1.44 N and its acceleration is -2.4 m/s².
a) Calculate the mass of the ball.
b) Which of the following describes the effect of the force on the ball?
A: The ball is moving backwards.
B: The ball is slowing down, but moving forwards.
C: The ball is moving faster forwards.
D: The ball is slowing down, and moving backwards.
a) m = F ÷ a
= -1.44 N ÷ -2.4 m/s² = 0.6 kg
b) B: The ball is slowing down, but moving forwards.
A boat has a mass of 400 kg.
It has a 900 N thrust acting on it, and a 600 N drag.
Calculate the acceleration of the boat.
resultant force = 900 N - 600 N = 300 N forwards
mass = 400 kg
acceleration = F ÷ m = 300 N ÷ 400 kg
= 0.75 m/s²
Calculate the resultant force that causes a 1.2 kg mass to accelerate at 8 m/s².
F = m × a
1.2 kg × 8 m/s² = 9.6 N
Calculate the size of the mass that accelerates at 0.8 m/s² when the resultant force is 18.8 N.
m = F ÷ a
18.8 N ÷ 0.8 m/s² = 23.5 kg
Calculate the acceleration of a mass of 80 g when the resultant force is 0.6 kN.
a = F ÷ m
0.6 kN ÷ 80 g = 600 N ÷ 0.08 kg = 7500 m/s²
(kN × 1000 = N, g ÷ 1000 = kg)
What is the equation for acceleration, including the units?
acceleration (m/s²) = force (N) ÷ mass (kg)
a = F ÷ m
