Forces

Question 1

When two objects interact what can be said about the forces exerted on each other?

Answer 1

They are equal and opposite.

Question 2

What is resultant force?

Answer 2

When a number of forces acting at a point may be replaced by a single force that has the same affect as motion as the original forces.

Question 3

A resultant force may cause an object to what?

Answer 3

Change in its state of rest or motion.

Question 4

If the resultant force acting on a stationary object is zero, the object will…

Answer 4

…remain stationary.

Question 5

If the resultant force acting on a stationary object is not zero, the object will…

Answer 5

…accelerate in the direction of the resultant force.

Question 6

If the resultant force acting on a moving object is zero, the object will…

Answer 6

…continue to move at the same velocity.

Question 7

If the resultant force acting on a moving object is not zero, the object will…

Answer 7

…accelerate in the direction of the resultant force.

Question 8

Equation for acceleration (force).

Answer 8

F = ma or a = F/m

Where:
F is force (N)
m is mass (kg)
a is acceleration (m/s^2)

Question 9

Velocity is…

Answer 9

…the speed of an object with direction.

Question 10

Acceleration equation (velocities).

Answer 10

a = (v-u)/t

Where:
a is acceleration (m/s^2)
v is final velocity (m/s)
u is initial velocity (m/s)
t is time (s)

Question 11

Gradient of distance/time graphs represents what?

Answer 11

Speed.

Question 12

Gradient on velocity/time graphs represents what?

Answer 12

Acceleration.

Question 13

When a vehicle travels at a steady speed, what can be said about the resistive forces and the driving forces?

Answer 13

They are balanced (no resultant force).

Question 14

The greater the speed of a vehicle the greater the what is needed to stop it in a certain distance?

Answer 14

Braking force.

Question 15

The stopping distance of a vehicle is a sum of what?

Answer 15

The driver’s thinking distance plus the braking distance.

Question 16

A driver’s reaction time can be affected by what?

Answer 16

Tiredness, drugs and alcohol.

Question 17

When the brakes of a vehicle are applied what happens?

Answer 17

Work done by the friction force between the brakes and the wheel reduce the kinetic energy of the vehicle and the temperature of the brakes increases.

Question 18

Braking distance can be affected by what factors?

Answer 18

Adverse road or weather conditions and poor condition of the vehicle (brakes or tyres).

Question 19

The faster an object moves through a fluid the greater the…

Answer 19

…frictional force acting on the object.

Question 20

An object falling through a fluid will initially…

Answer 20

…accelerate due to the force of gravity.

Question 21

Eventually the resultant force of an object falling through a fluid will reach…

Answer 21

…zero and the object will be moving at its terminal velocity (steady speed).

Question 22

Weight of an object equation:

Answer 22

W = mg

Where:
W is weight (N)
m is mass (kg)
g is gravitational field strength (N/kg)

Question 23

A force acting on an object may cause it to what?

Answer 23

Change shape.

Question 24

When a force is applied to an elastic object, such as a spring, the object will…

Answer 24

…stretch and stored elastic potential energy.

Question 25

For an object that is able to recover its shape, what happens (elasticity)?

Answer 25

Elastic potential energy is stored in the object when work is done on the object to change its shape.

Question 26

The extension of and elastic object is directly proportional to what?

Answer 26

The force applied, provided that the limit of proportionality is not exceeded for the object.

Question 27

What is the formula for extension of an elastic object?

Answer 27

F = ke Where: F is force (N) k is the spring extension (N/m) e is the extension (m)